# User talk:ScienceApologist/Optics workshop

To-do list for User:ScienceApologist/Optics workshop:
 Here are some tasks you can do:
1. Resolve the "etymology question". Should we include the etymology of optics in the lead or no?
2. Reference slow light?
3. Add Gaussian optics section that explains the thin lens and the mirror equations.
4. Add information about how the microscope and reflecting telescopes were improved.
5. Add summary paragraph to History section.
6. Prove $\frac{{\rm d}n}{{\rm d}\lambda} < 0,$ (reference Jackson, perhaps?)
7. Mention Faraday in the polarization section.

## Working here

Hi, using Wikisource as a working area is OK with me, and other users have done this type of thing in the past. One potential problem that we need to avoid is we like to keep our Template namespace very clean. Sometimes we want the en.wp templates, but sometimes we dont. So if you want a template imported, please mention it here first, and I will import it from en.wp if it is suitable, or find some other solution. 14:57, 12 March 2009 (UTC)

## Templates requested

Done 06:29, 6 April 2009 (UTC)

## Paragraph preservation

The following paragraphs dropped from the lead during editing. They're quite valuable and belong in the article a bit later on: Some optical phenomena depend on the [[quantum]] nature of light relating some areas of optics to [[quantum mechanics]]. In practice, the vast majority of optical phenomena can be accounted for using the classical electromagnetic description of light, as described by [[Maxwell's equations]], resorting to phenomenological rules (e.g. Beer's Law, constitutive equations) to describe the interaction of light with matter. Even when still completely classical, complete electromagnetic descriptions of optical behavior are often difficult to apply to practical problems. This is why particular simplified models are used instead, notably those of [[geometrical optics]] and [[physical optics]]. These limited models adequately describe large subsets of optical phenomena while ignoring behavior that is insignificant for the system of interest.<ref name=McGrawHill /> The pure science of optics is called optical science or [[optical physics]] to distinguish it from applied optical sciences, which are referred to as [[optical engineering]]. Prominent subfields of optical engineering include [[lighting|illumination engineering]], [[photonics]], and [[optoelectronics]]. Some of these fields overlap, with nebulous boundaries between the subjects terms that mean slightly different things in different parts of the world and in different areas of industry.<ref>{{cite web|title=SPIE society|url=http://spie.org/}}</ref> A professional community of researchers in [[nonlinear optics]] has developed in the last several decades due to advances in [[laser|laser technology]].<ref>{{cite book|title=The principles of nonlinear optics|author=Shen, Y. R.|publisher=New York, Wiley-Interscience|date=1984}} </ref>

## Speed of light

It would be good to state explicitly that light moves more slowly when it is not in a vacuum. Durova (talk) 05:58, 28 March 2009 (UTC)

This issue is one of the "triply complicated" problems I see a lot in science articles: It roughly goes as follows:
1. Zeroeth order: Those completely unaware that the speed of light is special.
2. First order: Those who are aware the speed of light is special, but think it is constant without qualification.
3. Second order: Those who are aware that the speed of light slows down in a refractive medium.
4. Third order: Those who realize that what really changes in the medium is not what is usually referred to as "the speed of light" as it appears in relativity and quantum electrodynamics, but it instead refers to a phase velocity which is a classical macroscopic feature of wave mechanics. The changing phase velocity is recovered in the limit where relativity/QM approach classical mechanics.
However, IMO, proper treatment of this is far too complicated for our optics article. Wikipedia has an article on slow light which we probably should link to (and that article probably should make these distinctions clear), but I'm not sure that this particular article would benefit from explaining away all three misconceptions.
ScienceApologist (talk) 01:45, 8 April 2009 (UTC)
Now I'm curious: here it says that in a vacuum, the phase velocity and group velocity are both the same and are equal to c. The phase velocity is lower in a medium with refractive index greater than 1. But, what is the group velocity in such a medium? Is it still c? Also, why is the phase velocity lower? Can it be it explained by virtual absorption by the atoms?
Slow light is a different phenomenon, but I think in this article it would be good to state what the phase velocity and group velocity are in an ordinary medium with refractive index greater than 1. It wouldn't take up too much space, and wikilinks to phase velocity and group velocity articles would be enough to explain what is meant. I think it's good to include facts like this (e.g. about Brewster's angle) to avoid having an article that many readers will find contains only things they already know. Coppertwig (talk) 14:37, 11 April 2009 (UTC)
A detailed answer to your question is essentially based on the properties of the medium you are considering. Generally, the group velocity is the slope of the dispersion relation while the phase velocity is the speed that a certain wavelength of electromagnetic disturbance has in the medium. The phase velocity is lower simply because the wavelength of light is shortened at a given frequency by the dialectric constant in the medium. One cannot simply state what the "phase velocity and the group velocity in an ordinary medium" is without specifying the characteristics of the dispersive properties and the index of refraction. The article actually deals with this in the simplest way possible at this point. Not sure what else to do. User:ScienceApologist 19:57, 15 April 2009 (UTC)

## Suggestions

• I'm not sure the etymology of the word belongs in the lead. Seems more appropriate to put that in Wiktionary.
• I like including etymologies in leads of articles. Not being a dictionary means we don't have articles that are merely definitions; I don't think it means we can't also include definitions (and etymologies etc., when interesting, as I think it is here.) Coppertwig (talk) 14:40, 11 April 2009 (UTC)
• "To describe certain situations, classical optics has to be abandoned in certain situations..." Redundant wording.
• There are several sentences under the Optical instruments and Physical optics sections that would benefit from citations.

Kaldari (talk) 20:03, 2 April 2009 (UTC)

• I was told in the last FA I did to include the origin of the term. I tend to agree with you though.
• Fixed.
• Fixing.

User:ScienceApologist

I think etymology rarely belongs in the lead of an article (and never in the first sentence). The exceptions are cases where the etymology is interesting or important in some way. Maybe someone would argue that to be the case here.--Srleffler (talk) 03:44, 8 April 2009 (UTC)
Don't know. It's mainly a holdover from the article as it appears on Wikipedia. Moreover, word origin is important to many people. We explain the origin of the word diffraction in this article too, which is actually a little more interesting (to me, anyway). ScienceApologist (talk) 04:48, 8 April 2009 (UTC)

## The article

You're doing a great job. :) Keep it up. Synergy 21:02, 2 April 2009 (UTC)

## Logic?

I've not been able to figure out exactly what this means (what follows what), in the "History" section of the article:

This experiment lead to a theory of diffraction for light and opened an entire theory of physical optics. This was the optical theory that was successfully unified with electromagnetic theory by James Clerk Maxwell in the 1860s.

In the second sentence, what does "This" refer to? And if it refers to the theory of physical optics, why would an experiment "open" that field ("re-open"? "enlarge"? "open for review"? "open for expansion?" "open for rexamination?") when it had been successfully unified with another field?

The second "this" antecedent is meant to be "physical optics" while the first "this" antecedent is meant to be Young's Double Slit Experiment. The experiment led to a development of a consistent theory for diffraction which allowed for a consistent theory of physical optics. It was physical optics with its assumption that light was a wave that would be unified with electromagnetism in the 1860s. User:ScienceApologist

Also, this doubling back - "A happened in the area of B, and, previously, B was C", is logically hard to follow. If "B was C" happened previously, it seems better to state it earlier in the article. 68.48.107.77 13:11, 3 April 2009 (UTC)

Agreed. The wording should be changed. User:ScienceApologist
I've tried a small reword :-) Privatemusings (talk) 23:48, 7 April 2009 (UTC)
I liked it, but I found some slight problems, so I reworded the reword. Hope you think it's okay. ScienceApologist (talk) 01:37, 8 April 2009 (UTC)

## Moving this to Wikipedia.

I am prepared to move this to Wikipedia, but I'd want to do it right, I think it likely that someone else here has more experience, who could do it or tell me how. I have not verified the sources, but the article is so much above normal Wikipedia standards, and the article completely free of apparent problems related to the SA ban, that I would transfer it and set up a process for source verification on the article Talk page. I highly doubt that any problems will be found, so what might otherwise be necessary caution seems to be counterbalanced by the apparent benefit to the project. Good work, SA.

Elsewhere, I have stated how SA could make otherwise clearly appropriate edits to Wikipedia as an IP editor, that continues to apply (for him and for all banned editors). Consensus, where it was discussed, was that these would not violate the ban. Essentially, a reasonable edit is made, and is self-reverted with a note like "Self-revert per ban of [editor name]." This would reveal IP, but if there were no non-self-reverted edits from that IP, reasonably attributed to the same editor, I'd vigorously defend against blocks based on ban violation from edits like that. --Abd (talk) 16:28, 4 April 2009 (UTC)

Thank you very much for your enthusiasm. Please respect our decision to work on it this way; a lot of thought and attention went into the current solution. Durova (talk) 17:28, 4 April 2009 (UTC)
The content should only be moved to Wikipedia by SA himself/herself. For a content edit of this size, GFDL licensing requires that the author receive proper attribution, and the best way to do that is to have the author make the edit themselves and be listed in the article history. I'll be happy to temporarily lift SA's siteban myself whenever he or she is ready to move it. Kaldari (talk) 03:31, 6 April 2009 (UTC)
That's fine with me. Durova had asked for help, I saw that, and just wanted to offer. Good luck. --Abd (talk) 05:27, 6 April 2009 (UTC)
Will that suffice? I see that not all of the edits on the history list come from SA's account. The GFDL requires all previous authors to be attributed, and all changes to be logged. It's not clear to me how one does that in this case. Conversely, if the argument is that those contributions and changes can be handled by reference to this page and its history, then the same would be true of SA's contributions.
Can an administrator lift a ban imposed by the arbitration committee? A ban is not a block.--Srleffler (talk) 17:02, 7 April 2009 (UTC)
Hold on a second. Wikisource is a GFDL site. Anything released to Wikisource is GFDL is licensed to wikisource. Under the terms of the GFDL wikisource can GFDL license anyone else. There is no reason to agonize here, this would be the same as wikipedia copying source code from a the Free Software Foundation's website. Jbolden1517 (talk) 19:47, 7 April 2009 (UTC)
Sort of, except attribution is needed for GFDL to be satisfied. You can't just copy wholesale without letting the reader know where the material came from so they can check who wrote it. This can be accomplished in a number of ways, and we're still trying to figure out which way is best.
The reason for this is both legal and useful from a research perspective. If I ever question a Wikipedia fact, I can check what IP or user account added the wording I'm wondering about by clicking on the history section. In the case of porting this entire text over to Wikipedia, we're lying about who created the text. There are a number of possible solutions to this. We'll keep you informed.
ScienceApologist (talk) 01:35, 8 April 2009 (UTC)
Actually that is not the case see section 11 [1]. Jbolden1517 (talk) 01:22, 9 April 2009 (UTC)
What relevance do you think section 11 has? That newly-added section gives the Foundation the right to relicense WP under another license, which also requires attribution to be preserved. As far as I know, the Foundation has not yet opted to do so.--Srleffler (talk) 03:39, 9 April 2009 (UTC)
Yep. Expanding a bit on that, based on the WP article on the GFDL, the license requires the text to have associated with it a list of everyone who edited it, and a log of every change made. Within one Wiki, this is handled by the change log. If an article is moved from one wiki to another without the change log, the license is violated. The move violates the copyrights of the authors who contributed. This is true even though they released it under the GFDL, and the new project also uses the GFDL.--Srleffler (talk) 02:57, 8 April 2009 (UTC)
This is actually incorrect. Linking to the source revision, which contains the change history, is generally considered to be sufficient (both within the community, and by the Wikimedia Foundation as evidenced by statements from Erik Moeller and Michael Snow of the WMF). This is also allowed under the interpretation put forward by the Creative Commons folks and the FSF. Avruch (talk) 16:20, 8 April 2009 (UTC)
Another problem is that this page is probably temporary and may end up deleted. It all depends on how much of a stickler you are. Anyway, I'm sure we'll come up with a solution for this. ScienceApologist (talk) 18:26, 8 April 2009 (UTC)
I think the solution is not to delete this article. Lets stop worrying about the theory issues. How long until you feel "done enough" to move this over to wikipedia. Obviously you can copy wikipedia edits back here and others can copy the edits from here over there. Syncing every few days until one side or the other decides to fork. When is a good cut over point in your opinion? AFAIKT the article is essentially accepted as is to replace the current. Jbolden1517 (talk) 01:22, 9 April 2009 (UTC)
I'd like a more full critique of the article before we port. So far, most people seem to be focusing on the earlier sections. I get the impression that most of the editors who are volunteering to review this article have not yet read through it all the way. Additionally, there is some talk on requesting a peer-review on Wikipedia with a link here. If there are major changes that need to be made, then it's better not to port till they're all done, in my humble opinion. I just don't think enough eyes have looked at it, and I would like to continue to have access to the article to edit it. If we port now, my subsequent edits will have to be edited in by proxy and I'd rather not do that because it makes the collaboration more difficult (for example, when users who are not blocked start making copyedits at Wikipedia while I'm making simultaneous edits at Wikisource).
To be honest, ideally, I'd just be unblocked and would work on this article at Wikipedia. But I've discussed this with an arbitrator and another user offline and we've discovered a "no go theorem" for why I cannot be unblocked. The details are likely not interesting to you, but they can be had for the price of a private e-mail to me.
User:ScienceApologist 01:51, 9 April 2009 (UTC)
I've already said that I would unblock you, per WP:IAR, but only for a single edit. I would suggest that you implement Awadewit's suggestions below and then we move the article over. If we wait much longer, your fork is going to get stale (and overwrite too many legit edits on the live article). You should also be aware, that per Wikipedia policies, anyone on Wikipedia can then delete your edit with no adverse consequences (since you are a banned user). It's up to the community to decide whether or not to keep your edit, but I think they should at least be given a chance to consider it. Kaldari (talk) 17:43, 15 April 2009 (UTC)
And FWIW, the GFDL only applies to "significant" edits, all of which I assume are SA's. Copyedits, wording revisions, and small additions generally do not attract copyright protection. Kaldari (talk) 17:47, 15 April 2009 (UTC)

## Categories

I suspect that this will be included in one or more categories. I don't see any suggested ones at the bottom. Otherwise excellent work! Fyslee (talk) 16:49, 4 April 2009 (UTC)

Currently, the article is under two categories: Category:Optics and Category:Greek loan words. Otherwise, I could imagine the categories of Category:Optics might be useful which include Category:Electromagnetic radiation; Category:Atomic, molecular, and optical physics; and Category:Applied sciences. User:ScienceApologist

## Helping out

sup Hey, great idea, ScienceApologist! At first glance, the article looks great.

Would you like help? I could read through it and list any suggestions I might have, and/or edit it. I often tend to come up with lots of little suggestions about punctuation and stuff. For example, as I did here. Let me know if that would be helpful, and whether edits are invited. I'll try to remember to check back here for a reply. Coppertwig (talk) 22:30, 7 April 2009 (UTC)

I'd be glad to accept your help. Feel free to simply edit in small corrections. I check the diffs often and will fix any errors I see crop up. I truly believe in the collaborative spirit of Wikipedia as it was about 6 years ago when people still took the "anyone can edit" adage seriously. Today, people are too afraid to step on other people's toes. Since we have a record of all the diffs in the history of this article, there is no problem with you making a change or even a mistake because, joy of joys, anyone can fix it! ScienceApologist (talk) 01:31, 8 April 2009 (UTC)

OK, great! Here are some suggestions.

• discovery of light being electromagnetic waves: I could be wrong, but I think it was Faraday who figured this out first, and that because of a learning disability, he wasn't able to write it in the form of equations, which is why Maxwell got the credit for the equations. I remember reading about this in "The Mind's Eye" by Gordon Thomas(23:24, 10 April 2009 (UTC)) West. On a Google Books search just now I found this, which seems to support the same idea. [2] Understanding physics By David C. Cassidy p. 550
• Interesting. I'd be extremely surprised if Faraday actually knew about the displacement current, which is a key component to figuring out the proper EM formalism. Certainly, Faraday suspected that light was somehow related to magnetism, which is probably part of the reason Maxwell was able to make the conceptual leap so easily, but Faraday, I believe, did not really think of fields propagating in the way that Maxwell did.
• I have a surprise for you, then: see p. 448 here. Energy and empire: a biographical study of Lord Kelvin By Crosbie Smith, M. Norton Wise Edition: illustrated Published by Cambridge University Press, 1989 ISBN 0521261732, 9780521261739
• What I get from that source is that Faraday wanted to connect magnetic field production to electrostatics, but didn't spell out the details. Stokes then dismissed Faraday's idea since he didn't think a displacement current existed. It was Maxwell who took the displacement current seriously. I don't think Faraday really understood that his idea implied the existence of a displacement current, and I'm not sure the source can be used to show otherwise.
• Well, I hope Faraday can at least be mentioned as having done work which helped pave the way for Maxwell. "Maxwell's theory was not entirely new when FitzGerald took it up in the 1870s; its roots went back more than 40 years into the work of Michael Faraday and William Thomson (later Lord Kelvin)." p. 11. [3] The Maxwellians By Bruce J. Hunt Edition: illustrated Published by Cornell University Press, 2005 ISBN 0801482348, 9780801482342 See also mention of the "Faraday effect" on p. 12. Coppertwig (talk) 16:35, 12 April 2009 (UTC)
• Sure, Faraday's work on polarization is incredible, but maybe it's more relevant to the section on polarization?
• Incidentally, it's not quite relevant to this article, but I wonder if you've heard of Banana Doughnut theory. :-)
• "It is usually simpler to use one of the two broad simplifying assumptions" Is making these assumptions equivalent to using classical electromagnetism, or is it a further assumption? If the latter, I suggest "Of these, most can be adequately described using one of two simplifying assumptions". Either way, I suggest changing the wording somehow to make clear the answer to my question.
• It's a further assumption. Classical electromagnetism isn't so much an assumption as it is a framework.
• OK, I'm making the change I suggested.
• "Quantum optics deals with the best model of light scientists have developed to date: the photon." I really like this sentence: it reminds us that science may progress further and develop yet better models.
• psychology?? I hope it explains later in the article how this is related.
• Optical illusions.
• Ah!
• emission theory: Instead of the wikilink to wikipedia:Emission theory perhaps what you want is to link to wikipedia:Emission theory (vision). I suggest a few more words in this article to make it clear what emission theory is so not as many people will need to follow the wikilink to find out, e.g. double the length of the description "This theory of the active power of rays".
• Sounds good to me.
• I assume you mean it's wikipedia:Emission theory (vision) and have therefore changed it to this wikilink and inserted "the idea that visual perception is accomplished by rays of light emitted by the eyes".
• "the optical phenomena associated with pinholes and concave lenses": I think "the optical phenomena associated with pinholes" needs to be made more specific. Phenomena that can be described with ray theory? Phenomena that need wave theory to describe (i.e. diffraction)? Phenomena that need quantum mechnanics to describe (i.e. double-slit experiment)? Maybe just deleting the word "the" would be satisfactory here, so it doesn't sound as if it's saying all pinhole phenomena were being described.
• Deleting "the" is fine with me.
• OK, I'm deleting "the".
• "In Italy, Galileo greatly improved upon these designs the following year." OK, my curiosity is piqued. How about a few words telling in what way he improved the designs? "In 1668, Isaac Newton designed an improved reflecting telescope" Again, in what way was it improved? Half a sentence or even a word or two may be sufficient.
• This needs to be (re-)researched. I was summarizing another source and I don't remember the details.
• "The frequency of light waves is determined by the period of the oscillations of the emitter." I'm not convinced of this; I'm not convinced that the emitter (e.g. an atom) necessarily oscillates. I don't know. This is covered by quantum mechanics somehow. Maybe it's the other way around: the frequency is determined by the amount of energy to be emitted (which is determined by the available energy states in the atom) and, if the emitter oscillates, perhaps its period of oscillation is determined by the frequency of the light being emitted. Anyway, it's fine if you have a reliable source for it.
• This is actually correct inasmuch as light can be described as a wave. For the particle-approximation, it is still correct, though the oscillations are essentially related to the energy difference in the same way that a stiffer spring has more energy and vibrates more quickly than a "lankier" spring. The source at the end of the paragraph also indicates this.
• $v=\lambda \nu$ The v and the $\nu$ look almost the same as each other. At least, use the same font for v and $\nu$ in the text as in the equation, to help the reader tell which is which. (I'm making that change.) Possibly one of them could be put in bold font or something. (Probably not, as that might imply it was a vector or something.)
• Sometimes people use $f$ for frequency, but we use that a lot for focal length. I don't think there is anything for this.
• Maybe f could be used for both. I don't think focal length and frequency would come into the same equations. It could say "Here, f means focal length." Ah, well, maybe that would be just as confusing.
• "The law also implies that mirror images are parity inverted (i.e. left and right are interchanged)." Some book (possibly by Jay Ingram or somebody) discussed this as a paradox: If a mirror doesn't reverse top and bottom, why does it reverse left and right? What's the difference between the top-and-bottom of a mirror and the left-and-right of a mirror that would cause one to be reversed and not the other? The answer: actually, mirrors don't reverse left and right. They reverse front and back (i.e. the part of the image closest to the mirror versus furthest from the mirror). For example, if you stand on a mirror, your image has its feet higher than its head. It's only because we're nearly bilaterally symmetric that we imagine ourselves mapped onto our mirror image with left and right reversed; when we identify with the mirror image we tend to identify our right hand with the image's left hand, but only because our left and right hands look so similar to each other and because real objects rotate but do not reflect.
• There are aspects of this explanation that are correct. Perception of a "reflection" is based on symmetries always. The most general symmetry is actually a rotational symmetry so that clockwise and anticlockwise are different by a parity operation.

I've also made other minor changes in the article. By the way, I copied it to Wikipedia only clicking "preview", not "save page", so that I could follow wikilinks and stuff. I think you can do the same. (Log out, display it with "preview", leave it displayed in one browser window while you log back in to edit here in another browser window.) I hope to look at the rest of the article later. Generally, it's very good and was fun to read! Coppertwig (talk) 16:02, 8 April 2009 (UTC)

• Re "parity inverted": this is fine now; someone fixed it to say "which we perceive as a left-right inversion".
• Corner reflectors: I would think that a 2D corner reflector (two mirrors; for example if two walls of a room are mirrors and meet at an edge) would give a non-parity-inverted image, since reflection twice would reverse parity twice, returning it to the original parity; but that a 3D corner reflector (for example, if the floor is also a mirror and you're looking down into the bottom corner of the room) would reverse parity due to triple reflection.
• If you draw the ray-tracing diagram, I believe the rays still reflect only twice in a corner reflector.
• I've looked at this more carefully, and while I agree that there are three physical reflections, I believe that the "third" reflection, being mutually perpendicular to the other two, will not cause a third mirror image to form (since it is mutually perpedicular). Therefore, I think that the three corner reflector only has two parity operations. Of course, we can check this out by looking at one's image in a three-corner reflector. User:ScienceApologist
• OK, I arranged three mirrors mutually perpendicular. That was fun. Now I understand it better. After reflection in n mirrors, the parity is reversed if n is odd. The light does reflect in all three mirrors, so the parity is reversed for the corner image. The corner image is composed of about 8 parts, depending on the order in which the light encounters the various mirrors; these parts all form parts of one consistent image (e.g. one part might have an image of the right ear, another part an image of the left ear, etc., all arranged together to make a whole face.)
Suppose I'm facing north, looking at a mirror on the north wall; that there's another mirror facing up on a table between me and the wall; and another mutually perpendicular mirror to my left, facing east. If I look directly into the mirror on the wall, I see an ordinary mirror image, parity reversed. If I've placed my hand on the right (east) side of my head, this image also has the hand on the east side of the head, but north and south are reversed: the image is facing south instead of north. If I look down, I see an image of myself reflected in two mirrors. It has north and south reversed just as the first image, but also have up and down reversed: the top of the head is at the bottom. Due to the double reversal, parity is actually back to normal: I could rotate myself about an east-west axis that would make me coincide exactly with the image (any such rotation is impossible for a parity-reversed image). If I look near the corner, I see an image which is reversed in three directions: the same as the second image, plus an east-west reversal, so that the image is facing south; has the top of its head at the bottom; and unlike all the other images and reality, also has the hand on the west side of the head. This is a parity-reversed image. Coppertwig (talk) 18:03, 16 May 2009 (UTC)
• "Upright images formed by mirrors are always virtual, while inverted images are real and can be projected onto a screen." I'm not sure that this is true if more than one mirror is used (as with a corner reflector). Maybe it therefore needs to be made singular "An upright image formed by a mirror is always virtual". I find this sentence harder to digest than the rest of the article. Maybe it's fine, but maybe it could use some explanation to help the reader along, e.g. after "virtual" adding something like "as with an ordinary mirror, where the image is behind the mirror".
• Indeed, it is true for only one mirror.
• "where θ1 and θ2 are the angles between the normal (to the interface) plane": the interface is a plane; the normal is a line or ray, not a plane. I'm changing it to "... are the angles between the line normal to the plane of the interface" Coppertwig (talk) 23:24, 10 April 2009 (UTC)
• The interface need not be a plane. The normal is a line that intersects the surface at the point the ray does, and is perpendicular to the surface at that point. The surface can have any shape. This is important, because lenses have curved surfaces.--Srleffler (talk) 00:39, 11 April 2009 (UTC)
• Oh, you mean it can be curved. Right. I only meant that it's a 2-dimensional surface, not a line, and that the normal is a line, not a plane. I see you've changed it to "a line perpendicular to the surface at the point where the ray hits", which is fine. Coppertwig (talk) 14:18, 11 April 2009 (UTC)
• "some media have an index of refraction which changes" I'm changing to "... which varies gradually with position" to make it clear that you don't mean changing with time. Coppertwig (talk) 23:24, 10 April 2009 (UTC) You might want to consider using phrases such as "continuous spatial variation", "arbitrary spatial variation", or "heterogeneous". 14:18, 11 April 2009 (UTC)
• In refraction, I added "The focal length f is considered negative for concave lenses." (Though this wouldn't be true for concave lenses with lower index of refraction than the surrounding medium.) I suggest also adding, "Incoming parallel rays are focused by a convex lens into an inverted real image one focal length from the lens, on the far side of the lens. Rays from an object at finite distance are focused further from the lens than the focal distance; the closer the object is to the lens, the further the image is from the lens. With convex lenses, incoming parallel rays diverge after going through the lens, in such a way that they seem to have originated at an upright virtual image one focal length from the lens, on the same side of the lens that the parallel rays are approaching on. Rays from an object at finite distance are associated with a virtual image that is closer to the lens than the focal length, and on the same side of the lens as the object. The closer the object is to the lens, the closer the virtual image is to the lens."
• I'm fine with your addition, but others may think it runs afoul of summary style. My opinion is that more is always better, however, so add it in. User:ScienceApologist
• "The principle of superposition can be used to predict the precise shape of interacting waveforms through the simple addition of the disturbances." I believe this is not true of all waves, for example waves in water: nonlinear effects occur in some situations, I believe. This sentence seems to me to be asserting something about all waves, and needs specification. Can we assert that light waves always interact linearly? If so, it would help to insert at the beginning of the sentence something like "Since light waves interact linearly". Coppertwig (talk) 23:03, 11 April 2009 (UTC)
• This is true for all waves. User:ScienceApologist
• Maybe there's some definition of waves meaning some sort of ideal waves for which that's true. For waves in the real world, in general it's not true. For example, for waves in water, when they come near shore and begin to break the effects are nonlinear: higher-amplitude waves will break sooner. In the middle of the ocean, conceivably higher waves might be subject to more wind, because they stick up further, leading to nonlinear effects. For sound waves, larger amplitudes might lead to opening of cracks or other effects in a material. For some types of waves, larger amplitudes might lead to bumping into things. For waves of motion propogating along a rope, for small amplitudes equations are posulated which do behave linearly, but the more general solution involving forces which change direction significantly due to change of shape of the rope with the wave action are I believe nonlinear; I could be wrong on that. In any case, some statement, supported by a reliable source, to the effect that light waves add linearly, would be helpful here I think. Coppertwig (talk) 21:45, 25 April 2009 (UTC)
• Any waveform can be decomposed into an infinite series of waveforms. This is the foundation of Fourier Analysis and is true even for very non-linear systems. What causes problems in non-linear systems is that small scale disturbances which are in principle very difficult to measure can affect larger scales. This point, however, does not violate superposition which is completely general to all waves regardless of their origin, shape, or particular context. ScienceApologist (talk) 19:01, 23 May 2009 (UTC)
• SA, it's not clear to me that you are right here. (And I'm familiar with Fourier analysis.) In a nonlinear medium, the propagation of one wave can alter the medium in a way that affects the propagation of other waves. I'm pretty sure that violates the superposition principle, and probably the assumptions underlying Fourier analysis as well. Consider sum frequency generation. Two waves with frequencies w1 and w2 interact, and do not produce a wave that is the linear sum of the two waves, but instead produce a wave at frequency w1 + w2. Fourier analysis does not explain that: the linear superposition of waves with frequencies w1 and w2 has frequency components only at w1 and w2, and not at w1 + w2.--Srleffler (talk) 04:55, 24 May 2009 (UTC)
• Look at how beats end up forming. Yes, beat packets will form with the sum of frequencies, but that's a result of superposition all the same. ScienceApologist (talk) 16:24, 24 May 2009 (UTC)
• This is different from beats in a linear system. If you combine two waves with different frequencies, the superposed wave's amplitude will vary with time at the sum and difference frequencies. If you take the Fourier transform, however, you will see that only the two original frequencies are present. There are no Fourier components at the sum and difference frequencies, if the system is linear. In sum frequency generation (a nonlinear effect), the sum frequency is actually created. Two infrared waves can combine to produce green light. Beating of waves in a linear system won't do that.--Srleffler (talk) 03:47, 28 May 2009 (UTC)
• "where θ is the angular resolution": I can guess approximately what this probably means, but would appreciate a few more words or a wikilink to pin the definition down precisely.
• "to first null" I don't understand what this means. Coppertwig (talk) 17:23, 12 April 2009 (UTC)
• I'm intending to go through the last part of the article but I've been busy. Sorry. Possibly this weekend or next weekend. Coppertwig (talk) 21:45, 25 April 2009 (UTC)
• " Lower frequency waves spread at a slower rate than higher frequency waves, resulting in a spreading of the spectrum from high frequency being the most deflected to low frequency being the least deflected." (last sentence of caption of image with moving waves) I'm not convinced that this sentence is meaningful and valid with respect to that image. As far as I know, the image may be composed of two sine waves of similar, but not quite identical, frequency added together. Maybe I just don't know what you mean by "spread". There can be media in which lower-frequency waves propagate faster than higher-frequency waves, so is this figure caption asserting something about light (that lower-frequency light travels more slowly? or what?) or is it asserting something that's true of all waves with a mathematical form similar to what's shown? I've changed the wording in the earlier part of the figure caption. Coppertwig (talk) 17:44, 16 May 2009 (UTC)
• Not sure what you are finding confusing. The two sine waves in question have actually very different frequencies so that the effect can analyzed carefully.
• You mean its a product of two sine waves of very different frequencies? Not the sum of two such. Coppertwig (talk) 01:22, 23 May 2009 (UTC)
• Actually, products and sums are equivalent in complex analysis of waves. ScienceApologist (talk) 18:52, 23 May 2009 (UTC)
• I'm moving the image of light going through a prism further up so it doesn't collide with the next image and make a blank area appear in the text.
• I've changed "how the propagation constant of the situation changes" to "the propagation constant". I think in general the propagation constant is not changing with time; rather, the constant specifies how the amplitude of the waves changes (attenuates) as they propagate.
• "the features of the wave packet that change with the same frequency as the amplitude of the electromagnetic wave": How can something change with a frequency? How can a frequency be the same as an amplitude? I just don't understand what you're trying to say here.
• "In mineralogy, this property, known as pleochroism" It's not clear what, in which previous sentence, is being referred to by "this": birefringence? dichroism? or what?
• actually both, they don't disambiguate carefully because all they care about is the phenomenology normally.
• "In this way, physical optics recovers Brewster's angle". Sorry, I don't understand this sentence, although I see that a mention of Brewster's angle would be relevant given the previous sentence.
• Brewster's Angle is just a mathematical construct. Why it is phenomenologically important is the subject of physical optics.
• Would it make sense if "involves" is used instead of "recovers"? (I put that in.) I don't understand "recovers" in this context. Coppertwig (talk) 01:22, 23 May 2009 (UTC)
• "Recovers" is a common term whenever pointing out a second way of getting the same concept. For example, the phrasing, "Proposition P says that A implies B directly. Proposition Q says that A also implies C. Since, by Proposition R, C implies B, we recover Proposition P." ScienceApologist (talk) 18:52, 23 May 2009 (UTC)
• "In general it is possible to describe an observed wave field as the sum of a completely incoherent part (no correlations) and a completely polarized part." I'm not convinced of this. I think this can be done for either linear polarization or circular polarization, but not in general; that is, the "completely incoherent part" may actually be polarized in a sense that wasn't considered.
• When measuring polarization, one uses Stoke's parameters which, by definition, take into account every kind of polarization possible. Thus, the statement is true.
• I'm not convinced. Hmm. Are you claiming polarization of the light can be represented by three parameters: one for the amplitude of the incoherent part, one for the amplitude of the polarized part, and one parameter (or a few) to describe the type of polarization? In that case, "completely polarized" would have to sometimes include light that's somewhere between linearly and circularly polarized. (Elliptically polarized, I guess). Well, maybe it's true. Coppertwig (talk) 01:22, 23 May 2009 (UTC)
• Not sure if you convinced yourself or not, but it's true. ScienceApologist (talk) 18:52, 23 May 2009 (UTC)
• OK, but what exactly is true? I'd like "completely polarized" to be more precisely defined here. How about: "In general it is possible to describe an observed wave field as the sum of a completely incoherent part (no correlations) and a part which is completely polarized, (whether linearly, circularly or elliptically)." Would it be accurate like that? I would find it more acceptable, as the original seems to me to be claiming that you can always express it as an incoherent part plus a purely linearly polarized part. Coppertwig (talk) 21:35, 23 May 2009 (UTC)
• In general, polarization is a continuum between circular polarization and linear polarization. If you use elliptical polarization, you can incorporate both. Circular and linear polarizations are just "special kinds" of polarization and do not need to be identified specifically. ScienceApologist (talk) 16:24, 24 May 2009 (UTC)
• Faraday aside, you're claiming " the first discovery of polarization, by Erasmus Bartholinus in 1669." and then "polarization was first discovered in 1808 by the mathematician Etienne Louis Malus. ".
• The the second should be changed. Malus is generally attributed with discovering polarization because no one paid attention to Bartholinus. Kinda like the Vikings in the New World.
• OK, you've changed it to credit him with the first mathematical models of polarization. It's fine now. (except maybe for Faraday) Coppertwig (talk) 01:37, 23 May 2009 (UTC)
• Please explain why scattering in the atmosphere would cause polarization. What's asymmetric? Oh, wait, I get it: it's the scattered light that's polarized. I changed the wording so it sounds more as if it's talking about the scattered light, rather than the light that is continuing to pass through the atmosphere in its original direction.
• You got it.
• The first paragraph of Modern Optics almost makes me feel like starting a new career in one of those fields!
• I'm removing "stimulated emission of radiation", as it feels too repetitive when you get to the section on lasers a couple of paragraphs later.
• Stimulated emission is, however, the most important part of laser technology.
• Everyday optics: maybe move this section much earlier in the article; you might thus keep a little longer the attention of readers whose eyes glaze over when they come to equations etc.
• True... but I kinda like it's bookend quality.
• Right. I already contradicted myself below, anyway (re sunsets) so never mind. Coppertwig (talk) 01:22, 23 May 2009 (UTC)
• " There are, however, twenty times more rod cells than cone cells in the retina because the rod cells are present across a wider area": this doesn't sound right to me. I think there are cone cells covering all or almost all the retina. There may be rods only in a relatively small area around the edges of the field of vision, but if there are twenty times more rods, I think it must be mostly because over most of the retina, there are more rods per unit area than cones.
• The cones are much more concentrated in the fovia than elsewhere. You can convince yourself of this by having someone test your peripheral vision for color sensitivity (it is very low).
• I agree that there are more cones in the fovia. I agree that there are fewer cones in peripheral vision. I was reading "wider area" to be a claim that the surface area of the parts of the retina that contains rods is larger then the surface area containing cones (true, I believe) and that this was the reason there were 20 times more rods (very misleading, since I believe the surface area containing rods may be less than twice as large; this explanation gives the impression it's 20 times as large). I was perhaps misreading "wider area" as talking about surface area, when perhaps it only means that the rods extend further to the edges of the field of vision. In any case, I still disagree with your wording. I think the fovea is only a small part in the centre of the retina; I could be wrong about that. I believe that around that is the majority of the retina, containing both rods and cones, and then around that a smallish area with pretty much just rods. Are you claiming that the area of the retina containing rods is 20 times larger than the area containing cones? Coppertwig (talk) 01:22, 23 May 2009 (UTC)
• I am still confused as to what you are trying to say here. The fovea is quite small and contains mostly cones. The majority of the retina does not contain an equal number of rods and cones. ScienceApologist (talk) 18:52, 23 May 2009 (UTC)
• That's what I'm trying to say! I think most of the retina is composed of regions which have both rods and cones, and that if there are 20 times as many rods as cones, then I think the density (number per unit area) of rods must be much higher than those of cones, in those regions. I think the article seems to be saying something quite different from that, and needs to be reworded. I think this part needs to be changed: "because the rod cells are present across a wider area". I think it's misleading to claim that that's the reason there are 20 times as many of them. I think that's not the main reason. I think the main reason must be that there are more of them per unit area in most parts of the retina where both are present. (Assuming the 20 times as many is true. I didn't know that.) Coppertwig (talk) 21:35, 23 May 2009 (UTC)
• This is something of a semantics issue. I read rod cells being present over a larger area to mean that there are more rod cells in the retina. ScienceApologist (talk) 16:24, 24 May 2009 (UTC)
• Optical illusions section: the first paragraph mentions three types of optical illusions. The rest of the section should discuss those three types in the same order they were mentioned. I think it discusses only the third type, and then introduces two more types that hadn't been mentioned.
• Perhaps a bit confusing, but I'm not sure I can see a way to make it clearer. I'll try tweaking.
• "the reciprocity of the camera and the shot": not clear whether this means that there is a reciprocity between the camera and the shot, or whether it's referring to the shot, and also to the reciprocity of the camera.
• The camera has a quality called "reciprocity". It affects the shot.
• Then would it still make sense (but be less ambiguous) if it said "the shot and the reciprocity of the camera"? But then the following words should probably be "which are..." rather than "which is...". Coppertwig (talk) 01:37, 23 May 2009 (UTC)
• "The two ways to increase the f-stop": what does "f-stop" mean?
• F-stop is the scale on which you measure the f-number. It "stops" at various values on the dial.
• I put in "f-number or f-stop". Coppertwig (talk) 01:37, 23 May 2009 (UTC)
• Ending with a section on sunsets and rainbows gives a nice feel to the article. OK, I've gone through the main text part. I might or might not check the formatting of the references, etc. Coppertwig (talk) 01:00, 17 May 2009 (UTC)
• I suggest adding a paragraph or so about coloured objects. I mean, say you have a red book sitting on the table. You look at it and it looks red. Why? Is it because it absorbs all the colours of light except red? Or does it absorb light of other frequencies and re-emit it as red light? Why does it absorb certain frequencies of light: is it because to absorb light, you need molecules with possible excited states that electrons can move into, that require absorbing just that amount of energy to move into that state? Does a photon have a precise wavelength, or is there an uncertainty associated with it? What happens if a photon approaches an object that has possible excited states that would require almost, but not quite exactly, the amount of energy in the photon? When something looks yellow, what does that mean: it could be either yellow light (light with a particular wavelength, as from the part of a rainbow that looks yellow), or it could be a mixture of red light and green light, which our eyes react to the same way (or almost the same way?) as to yellow light. Or something like that. You could also perhaps put in a sentence or so about colour vision in species other than humans. I think birds have, interestingly, a better way to perceive colour than humans do. wikipedia:Color vision#In other animals Coppertwig (talk) 03:11, 18 May 2009 (UTC)
• This actually an issue of reflection versus absorption. A "blackbody" appears black because it absorbs light and a perfectly reflective body appears "white" because it reflects sunlight. A "blue" object appears blue because it reflects blue light most efficiency and absorbs blue light least efficiently (those are equivalent statements). Not sure where to include this point, but let me know if you can find a place. ScienceApologist (talk) 15:02, 22 May 2009 (UTC)
• Someone at Talk:Optics said, "Now the optics article is mainly composed of stuff from other wikipedia articles integrated and connected. The integrator (Science Apologist) ... " (meaning this article, I guess). If you've copied parts of the article from other Wikipedia pages (other than the Optics article, which I already know about), please say so so that we can make sure the original authors get attribution under GFDL. If that statement is wrong or I've misunderstood it then I apologize for repeating it. Coppertwig (talk) 01:50, 23 May 2009 (UTC)
• Occasionally, when writing subsections, I took some wording from the main articles referenced. That is very common practice in writing summary style and has been explicitly discounted as a GFDL problem in the past since the links are direct. ScienceApologist (talk) 18:52, 23 May 2009 (UTC)
• Thanks for the clarification. In future, when copying material from one article to another, I suggest following the procedure at en:wikipedia:WP:SPLITTING, i.e. mentioning in the edit summary a link to the article from which the material was copied, and also making a note at the other article so that it won't be deleted without consideration for the GFDL requirements. Coppertwig (talk) 21:35, 23 May 2009 (UTC)
• In general, SA, I'm very positively impressed with your constructive response to criticism on this page. I've enjoyed these discussions. Coppertwig (talk) 16:42, 24 May 2009 (UTC)

## two equations

The text presents two equations as alternates

$1 < n(\lambda_{\rm red}) < n(\lambda_{\rm green}) < n(\lambda_{\rm blue})\ ,$
$\frac{{\rm d}n}{{\rm d}\lambda} < 0,$

The second is much much stronger than the first from a math perspective, i.e. the second implies the first but not visa versa . I don't know the physics though. In practice does the 1st imply the 2nd? Like would this hold for way down or way up i.e. for gamma rays of different lengths or radio waves? Otherwise I think it should say something like "or alternately in the viable spectrum" or something less strong. Jbolden1517 (talk) 01:22, 8 April 2009 (UTC)

The first relation is more-or-less the observational result that people with a prism or even a piece of glass with changing thickness would see. The second condition can be induced from the first (though not for all wavelengths), and the relation can also be proven theoretically given a consistent model for refraction from electromagnetic theory and material science. In practice, most dispersive media follow this inequality for ranges of wavelengths that are more extensive than just the optical, and so include the adjacent regions of the ultraviolet and infrared, but the relation rarely holds for all wavelengths because, for example, gamma rays penetrate most matter as particles and long enough wavelength radio waves pass through most material with very little attenuation or dispersion. ScienceApologist (talk) 01:28, 8 April 2009 (UTC)
Do you have a ref for the relation can also be proven theoretically given a consistent model for refraction from electromagnetic theory and material science.? I would never induce the 2nd from the first. Just because a function is decreasing at 3 points (small ranges) clustered close together does not mean that it is decreasing everywhere. For example y=x^3-x is decreasing at 1/7, 1/6, 1/5 but spends most of its time increasing. But the material science issue allows you to treat those two as being close enough. I like your paragraph here better than the one in the article. Jbolden1517 (talk) 01:11, 9 April 2009 (UTC)
The derivation can be found in most upper-division undergraduate to graduate level E&M texts. Jackson is probably the best. I can dig out the page number if you'd like. As for the induction, the "three points" are just convenient stopping points on your way down the spectrum. There is a one-to-one mapping of the position of the color in the spectrum coming out of the prism and the index of refraction. This can be proved with the mathematics in the article and the picture of the triangular prism (if you believe the picture of the triangular prism). Since physical measurements of the wavelengths of optical light can be done in other ways, this sets the condition automatically.
If you want to replace the paragraph in the article with a better one, be my guest.
User:ScienceApologist 01:46, 9 April 2009 (UTC)
If I recall correctly, the second equation holds over all wavelength ranges where there is no absorption. This is a fundamental result, that can be derived directly from electromagnetic field theory and holds for all materials at all wavelengths where the EM theory works. Where there is absorption, dn/dλ can be greater than zero. Since optical materials typically have negligible absorption in the visible band, dn/dλ has to be negative there. Most optical materials have some absorption out in the mid-IR, so dn/dλ can be greater than zero for infrared light. Don't quote me on any of this though—it's been a long time since my last EM theory class.
It sounds like the text is confusing, and needs to be cleaned up, with reference to Jackson's book.--Srleffler (talk) 21:42, 9 April 2009 (UTC)

I did some searching last night. I see these equations (unsourced) on other wikipedia articles. I saw curves in a bunch of sources and d\lambda/dn didn't seem to be holding globally. I may be looking at anonymous situations, I don't know enough physics to know the usual from the unusual here. So I'm going to change to your paragraph and fact tag. Jbolden1517 (talk) 13:32, 9 April 2009 (UTC)

See above. I think the text is the right idea, but probably isn't explaining it correctly.--Srleffler (talk) 21:42, 9 April 2009 (UTC)

## Minor comments, and length of article (not so minor, perhaps)

Re this edit: the index of refraction is not a "formula". It is a physical property of the medium. We describe the physical property by a formula. I dropped the comment that it is unitless only because I couldn't find a convenient way to work that back into the sentence.

Re User:ScienceApologist/Optics workshop#Reflections: I don't think it is correct to say that the difference between specular and diffuse reflection is that one "maintains paraxiality". The law of reflection holds outside the paraxial approximation. I don't have time to work on the wording here now, though.

It seems to me that the article is probably too long. Sections cover subjects in detail, that are treated fully in articles of their own. WP:Summary style may be beneficial.--Srleffler (talk) 04:49, 8 April 2009 (UTC)

• Re:Paraxiality, I attempted to fix it. see what you think. ScienceApologist (talk) 04:56, 8 April 2009 (UTC)
• "Parallel to each other" doesn't work either. Not true for specular reflection off of curved surfaces. The difference between specular and diffuse is based on whether the surface, viewed at a macroscopic level, obeys the law of reflection. --Srleffler (talk) 05:10, 8 April 2009 (UTC)
• We can just say planarflat surfaces. ScienceApologist (talk) 06:22, 8 April 2009 (UTC)
• I'll take another stab at the wording. There has got to be a better solution than that. Arbitrarily limiting the definition of specular and diffuse reflection to flat surfaces is awful. --Srleffler (talk) 03:49, 9 April 2009 (UTC)
• I disagree that it's "awful". In fact, it's "awfully useful" when you are teaching students about the difference. User:ScienceApologist 17:32, 9 April 2009 (UTC)
• Re:Summary style, I think content forking may be a good idea, especially at the level of geometrical optics and physical optics. The challenge is deciding what content is necessary and what content is superfluous. This is an editorial judgment more than anything else. ScienceApologist (talk) 05:04, 8 April 2009 (UTC)
• I notice that most of the sections that have main articles linked are not in summary style. It seems to me that these sections need heavy pruning, to bring them down to a summary. This article should not go into great detail on the history of optics, or on topics such as reflection, refraction, interference, etc. Rather, it should present a top-level, easy to understand summary of the topics, leaving the details to the already-written articles on those subjects. Obviously content can be moved from here to those articles as well if there is material here that they lack.--Srleffler (talk) 03:49, 9 April 2009 (UTC)
• We need to be careful to make sure that all the content currently in the article is in the linked main article before we prune too much. This is not something we can do efficiently here, unfortunately. User:ScienceApologist 17:32, 9 April 2009 (UTC)

Another minor issue: overlinking. I noticed in my skim that many terms seemed to be linked more than once. Hopefully one of the automated editing tools can scan for those and delete the extras.

There are occasions where it is smart to slightly overlink. For example, when when a term appears early on and later on, it's a good idea to have two links in case someone has skipped to the relevant section using the TOC. User:ScienceApologist 17:32, 9 April 2009 (UTC)

## Section rewrite

I did a rewrite of one section, to get a better feel for where the text stands. The previous version contained:

• factual errors (retroreflectors minimize the scattering of the light rays)
• poor explanation (the distinction between specular and diffuse, for example)
• confusion of concept (confusing focus and focal point; describing specular reflection by the law of reflection, but diffuse reflection by albedo, without mentioning Lambert's law)
• too much detail, since the section references a "main" article on the topic

I'm not posting this to be critical, but rather as an indication of the issues to be looked at in the rest of the text. In particular, this is not a criticism of SA, who has worked hard on this. Writing a good science article is hard. I'm not sure anyone can do it alone. Things that seem perfectly clear and correct to one writer will contain flaws that only another person is likely to catch. It's especially hard in science, which often has to be understood on different levels (see the example in #Speed of light, above.) --Srleffler (talk) 05:06, 9 April 2009 (UTC)

This is actually a great list to keep in mind. I think we should incorporate it into a Scientific Standards policy page on Wikipedia as a reminder of the biggest pitfalls in writing science articles. User:ScienceApologist 19:14, 9 April 2009 (UTC)
I agree that writing a good article is hard. Just because I'm able to find some minor things to change doesn't necessarily mean I could write an article like that myself (or at least not without a tremendous amount of work). Coppertwig (talk) 22:43, 10 April 2009 (UTC)

## Gaussian optics?

While rewriting the section on reflection, I deleted the equations. Partly this was because I was trying to make the section a less-technical summary, leaving the mathematical detail to the main article on reflection. Partly, though, it was because I'm wondering if a different structure would be better. The formulas for image formation by a mirror are identical to those for lenses and even for whole optical systems (at least, given the appropriate sign convention). These simple, approximate, formulas are part of the approximation that is sometimes called "Gaussian optics". It might be better to collect them together earlier in the article, and explain it as a common technique for determining where an optical system forms an image, and how big it will be. This might, of course, end up being a full article on Gaussian optics, with a shorter summary in the main optics article.--Srleffler (talk) 05:16, 9 April 2009 (UTC)

Gaussian optics sounds like a great way to go and will simplify the mirror and lenses sections. We might include these ideas in the section currently titled "Approximations". User:ScienceApologist 17:29, 9 April 2009 (UTC)

I have been asked by ScienceApologist to copyedit this article. As I am unfamiliar with this topic, I am reticent to change much text, so I will leave a list of questions as I go. I would appreciate it if someone would check over the copyedits I do make to make sure that I have not introduced an inaccuracy into the article. If the editors could respond under each comment, I would appreciate it.

• including its interactions with matter and its detection by instruments - "detection by instruments" sounds strange to me. I'm trying to figure out why - it has a slight SF and aliens quality about it somehow. "Captain, none of our instruments can detect the nanites!" Awadewit (talk) 02:43, 14 April 2009 (UTC)
• The "by instruments" is probably redundant. We can safely remove it and keep the meaning, methinks. User:ScienceApologist
• The word optics comes from the ancient Greek word ὀπτική, meaning appearance or look - A fascinating fact, especially to someone like me who is interested in historical linguistics, but is it absolutely necessary in the lead? Awadewit (talk) 02:43, 14 April 2009 (UTC)
• Optics usually describes the behavior of visible light as well as infrared and ultraviolet light, which are similar to visible light but are not detectable by the naked human eye. - Does "optics" always mean "the study of optics" or do we need to say "The study of optics" or some such each time? Awadewit (talk) 02:43, 14 April 2009 (UTC)
• No, sometimes "optics" refers to the system. For example, "The optics of this camera are superb!" I can see our way to changing that wording. User:ScienceApologist
• which are similar to visible light but are not detectable by the naked human eye - I see that you have said "naked human eye" since the assisted human eye can see infrared and ultraviolet, but I wonder if this is implied by the phrase "human eye" itself? Awadewit (talk) 02:43, 14 April 2009 (UTC)
• The "assisted human eye" can detect essentially everything. I think that "naked" human eye is probably redundant, but this is an issue best left to the lay reader, so I defer. User:ScienceApologist
• Classical electromagnetism can be used to describe most everyday optical phenomena - "can be used" or "is used"? Awadewit (talk) 02:43, 14 April 2009 (UTC)
• Of these, most can be adequately described using one of the two broad simplifying assumptions for describing light: to treat light as a ray or as a wave. - This is wordy. How about this rewording: Most can be adequately described by assuming that light is either a ray or a wave. Awadewit (talk) 02:43, 14 April 2009 (UTC)
• How about, Most can be adequately described by assuming that light is either simply a ray or a wave.? User:ScienceApologist
• Physical optics was developed during the 19th century and accounts for the wave-like nature of light, which is needed in particular to explain interference and diffraction. - I feel like this could be phrased better. How about something like: Physical optics, which was developed during the 19th century, in order to account for interference and diffraction represents light as a wave. (I have no idea if this is correct.) Awadewit (talk) 02:43, 14 April 2009 (UTC)
• How about, Developed during the nineteenth century, physical optics accounts for diffraction and interference by modeling light as a wave.? User:ScienceApologist
• Together, geometrical and physical optics encompass classical optics, a system of models capable of describing and predicting many optical phenomena. - Must we say "optical phenomena" - isn't that understood? Awadewit (talk) 02:43, 14 April 2009 (UTC)
• I have a question about the lead. If I only read the lead of this article, I would be slightly confused regarding the validity of geometrical and physical optics. I know, for example, that classical mechanics holds in many situations, but that it is not a comprehensive model. It has been supplemented by quantum mechanics. However, I am not totally sure to what extent quantum optics has superseded classical optics from this lead. Is it an analogous situation? You might also want to consider a readership who lacks that analogy to go on. I think they might be even more confused than I. Awadewit (talk) 02:43, 14 April 2009 (UTC)
• Yes, it is very much analogous. Part of the issue is that there are so many different ways to treat optics. Geometrical optics is, in a sense, completely developed (it was described by Feynman as the only area of physics in which there are no new discoveries left to be made). However, the more complicated and "non-linear" the models get the more mysteries end up cropping up. Though the more complicated models can account for phenomena the simpler models simply cannot explain, they also make predictions and have "nooks and crannies" that are yet to be fully explored. Essentially, the more complicated the model, the less well-explored it is. This is the case in most broad categories of physics. We could make the same statement about dynamics, for example. I don't know if this helps at all, but that's my take. Not sure what we should do about this issue just yet. User:ScienceApologist

### History

• In my opinion, the "History" section meanders a bit. Could you perhaps add a summary paragraph at the beginning and some guideposts throughout the section so that the reader knows where the section is headed? Otherwise, the reader feels a bit at sea, surprised at each new topic. I thought that this was a particularly good transition: Newtonian optics and emission theory was generally accepted until the early 19th century. Awadewit (talk) 03:50, 14 April 2009 (UTC)
• This will require a bit more time than I have at the moment, but it is a good idea. User:ScienceApologist
• Optics began with the development of lenses by the ancient Egyptians and Mesopotamians, followed by theories of light and vision developed by ancient Greek and Indian philosophers, and the development of geometrical optics in the Greco-Roman world. - The word "developed" is overused here. How does this rewording sound: Optics originated with the invention of lenses by the ancient Egyptians and Mesopotamians, followed by the development of theories of light and vision by the ancient Greek and Indian philosophers, and finally the beginnings of geometrical optics in the Greco-Roman world. Awadewit (talk) 03:50, 14 April 2009 (UTC)
• The third paragraph of the "History" section doesn't seem to have a clear topic - it doesn't cohere as a paragraph. I would suggest either rewriting the paragraph to explain more clearly why this material is related or break up the paragraph and place the information in more relevant locations. Awadewit (talk) 03:50, 14 April 2009 (UTC)
• What do you think about combining the telescope and microscope paragraphs? You could place that new paragraph in the context of the importance of lens development, a phenomenon which just a bit obscured right now. Awadewit (talk) 03:50, 14 April 2009 (UTC)
• Optical theory progressed in the mid-17th century with treatises written by philosopher René Descartes, which explained a variety of optical phenomena including reflection and refraction by assuming that light was emitted by objects which produced it. - I find this sentence slightly confusing. I think it is the placement of the "by assuming" clause. Could you reorder the sentence to perhaps highlight the connections Descartes was making more clearly? Awadewit (talk) 03:50, 14 April 2009 (UTC)
• Optical theory progressed in the mid-17th century with treatises written by philosopher René Descartes. He explained a variety of optical phenomena including reflection and refraction by assuming that light was emitted by objects which produced it. Does that work? User:ScienceApologist
• In 1690, Christian Huygens proposed a wave theory for light based on suggestions that had been made by Robert Hooke in 1664. - Could you expand on this? Awadewit (talk) 03:50, 14 April 2009 (UTC)
• Well, Robert Hooke thought everything was a spring. He modeled light as a spring. Of course, light isn't a spring, it's a wave, but there is a deep connection between harmonic motion of springs and the harmonic oscillations contained in light waves. To this end, Hooke presaged Huygens' principle and Huygens essentially took Hooke's side of the Newton-Hooke debate (a debate that was so virulent that Hooke went to his grave without being on speaking terms with Newton). When Huygens took up the cause, Newton had had enough and published Opticks in a fit of pique. Opticks essentially outlines all the details of geometrical optics but uses corpuscles to explain dispersion in a way that cannot consistently explain diffraction and interference. Of course, it wouldn't be until Fresnel showed the equivalence of ray and wave optics more than 100 years later that people decided that Newton was probably a bit too hasty in his dismissal of Huygens-Hooke. User:ScienceApologist
• Newtonian optics and emission theory was generally accepted as correct until the early 19th century - Are these two different ideas? Should this be "Newtonian optics and emission theory were"? Awadewit (talk) 03:50, 14 April 2009 (UTC)
• I think that the last three paragraphs of the "History" section will be hard for someone without a background in physics to understand, however I do not think that it is possible to overcome this, as you cannot explain all of the necessary concepts in this short space. You will lose some readers at this point. This raises the question of whether you should move the "History" to the end of the article, foregrounding the actual physics itself, so that any readers who drop out of the article early have actually read about the physics of optics. Something to consider. Awadewit (talk) 03:50, 14 April 2009 (UTC)

### Classical optics: Geometrical optics

• Classical optics works by modeling light as an electromagnetic wave composed of oscillating electric and magnetic fields. These fields continually generate each other according to Maxwell's equations as the wave propagates through space and oscillates in time. - How about: Classical optics models light... Awadewit (talk) 04:16, 18 April 2009 (UTC)
• Light propagates through space as a wave with amplitudes, wavelengths, frequencies, and speeds that are unique to how it was emitted and the particular conditions of the material through which it is propagating. - I find the tense shifts in this sentence awkward. Generally, sentences are supposed to remain in a single tense. Is there a way to write it that way? Awadewit (talk) 04:16, 18 April 2009 (UTC)
• Light propagates through space as a wave. The amplitudes, wavelengths, frequencies, and speed of light are affected by how light is emitted and the particular conditions of the material through which it is propagating. ScienceApologist (talk) 20:23, 20 April 2009 (UTC)
• The frequency of light waves is determined by the period of the oscillations of the emitter. While the frequency of a light wave does not normally change as light travels through different materials, called optical media, the wavelength of light is affected by the indexes of refraction in different media. - This sentence is introducing a lot of terms to the reader unfamiliar with this topic - must we introduce "optical media"? Awadewit (talk) 04:16, 18 April 2009 (UTC)
• The amplitude of the light wave is related to the intensity of the light which is related to the energy stored in the electric and magnetic fields of the light wave. - Dare I ask "related how"? Awadewit (talk) 04:16, 18 April 2009 (UTC)
• Well, for classical electrodynamics, the amplitude of a simple light wave is the square root of the intensity divided by two (since half of the energy is in the magnetic field and half is in the electric field). This might be a bit much for the casual reader, but, again, I defer. ScienceApologist (talk) 20:23, 20 April 2009 (UTC)
• The "ray" in geometric optics is an abstraction, or "instrument", that can be used to predict the path of light. - "can be used" or "is used"?
• A light ray is a ray that is perpendicular to the light's wavefronts (and therefore collinear with the wave vector). - 1) A ray is a ray? Usually we try not to repeat the word itself in the definition, as the definition is supposed to clarify to the uninitiated. 2) I am unsure what "collinear with the wave vector" means.
• A "light ray" is a "geometrical ray". It's like saying "A line-of-sight" is a "line drawn between an observer and the object they are observing". The term "light ray" is meant to be what is being defined. Maybe we should italicize it as light ray so it's more obvious? Not sure. ScienceApologist (talk) 20:23, 20 April 2009 (UTC)
• Geometrical optics provides rules for propagating these rays through an optical system, which indicates how the actual wavefront will propagate. - This wording indicates to me that geometrical optics tells us how to "send" light through stuff. :) Is that right? Awadewit (talk) 04:16, 18 April 2009 (UTC)
• It tells us how light will travel through stuff and therefore, if you want light to get to a certain location, you use the geometrical optics. Perhaps a better wording would be Geometrical optics provides rules that describe how light rays and their associated wavefronts propagate through an optical system. ScienceApologist (talk) 20:23, 20 April 2009 (UTC)
• A slightly more rigorous definition of a light ray follows from Fermat's principle which states that the path taken between two points by a ray of light is the path that can be traversed in the least time - It is unclear to me if this definition is used in geometrical optics. Also, it is its own little paragraphs, marooned. If it is important, please integrate it more seamlessly to the article. Awadewit (talk) 04:16, 18 April 2009 (UTC)
• It is extremely important from a basic physics standpoint. It stands alongside the principle of least action and the principle of least distance as one of the defining features of physics (and is also seen in quantum electrodynamics as well!). I'll think about how to integrate it elsewhere. ScienceApologist (talk) 20:23, 20 April 2009 (UTC)
• Geometrical optics is often simplified even further by making the paraxial approximation, or "small angle approximation." - Since this is the first sentence of a section, it should be clearer what the "even further" is referring back to. Awadewit (talk) 04:26, 18 April 2009 (UTC)
• I don't understand the "Approximations" section. I don't know if this is one of those sections that it is impossible for me to understand or not. Just letting you know. The problem probably lies in the fact that the last time I really studied mathematics was about 15 years ago and that was just basic calculus. Awadewit (talk) 04:26, 18 April 2009 (UTC)
• Not sure. This section is kinda cumbersome, I agree. At some point, we'll probably want to include some commentary on Gaussian approximations of optical devices as seen in the ToDo list. Maybe things will get fixed then. As it is now, I'm not sure what to do exactly. ScienceApologist (talk) 15:20, 22 May 2009 (UTC)
• This is known as the Law of Reflection. - Is there a way to integrate this information more seamlessly into the paragraph? Awadewit (talk) 04:26, 18 April 2009 (UTC)
• Not sure. It flows like a classic proof. A means B. B means C. A implies C. We call this deduction P. ScienceApologist (talk) 15:20, 22 May 2009 (UTC)
• The magnification of a flat mirror is unity. - What does "unity" mean here? Awadewit (talk) 04:26, 18 April 2009 (UTC)
• "One". It is fairly common in mathematical writing to say this instead of "one", which is considered more ambiguous stylistically. ScienceApologist (talk) 15:20, 22 May 2009 (UTC)
• 'This phenomenon is called total internal reflection and allows for fiber optics technology - Why does it allow for fiber optics technology? Awadewit (talk) 04:55, 18 April 2009 (UTC)
• Because otherwise the light would leak out of the fiber. This way it is totally reflected back into the fiber. Added a sentence to this effect. ScienceApologist (talk) 15:20, 22 May 2009 (UTC)
• Another refraction scenario of note is the situation where the refracted ray and the reflected ray form a right angle. - This sentence needs to be reworded to emphasize the "right angle", which I presume is the important part of the sentence. Phrases such as "another scenario of note" do not make it clear why the situation is important. Surely there must be many scenarios of note! Why is this one worth mentioning? Awadewit (talk) 04:55, 18 April 2009 (UTC)
• I tried. The importance of Brewseter's Angle is the production of polarized light. ScienceApologist (talk) 15:20, 22 May 2009 (UTC)
• The discovery of this phenomenon when passing light through a prism is famously attributed to Isaac Newton. - This is an odd phrasing - "famously attributed to Newton" - it suggests that the discovery was only attributed to him and that he did not really make it. Is that the case? Awadewit (talk) 04:55, 18 April 2009 (UTC)
• People have been seeing rainbows for centuries. It's kinda like the way we claim Newton "discovered" gravity. He was just the first to systematically describe it. ScienceApologist (talk) 15:20, 22 May 2009 (UTC)
• The detailed prediction of how images are produced in these lenses can be made using ray-tracing similar to curved mirrors. - Are the images produced in the lenses? Awadewit (talk) 04:55, 18 April 2009 (UTC)
• The objective focuses an image of an object that is essentially at infinity at its focal point which is adjusted to be at the focal point of an eyepiece which is generally of a much smaller focal length. - I found this sentence a bit hard to follow - what does the "at infinity at its focal point" mean?

### Classical optics: Physical optics

• Just so you know, I found this section extremely difficult to follow. Many of the terms I am unfamiliar with and I tired of looking them all up on Wikipedia (which didn't always help). I'm not sure this is a resolvable problem, but you should be aware that I really started to get lost in this section, particularly beginning with the "Dispersion and scattering" subsection. Awadewit (talk) 02:20, 26 April 2009 (UTC)
• This is good to note. I'm also not sure what to do about this, but it is a might unfortunate. ScienceApologist (talk) 16:09, 22 May 2009 (UTC)
• this explains how optical phenomena are manifested when there are multiple sources or obstructions that are spaced at similar size as the wavelength of the light - I don't quite understand "that are spaced at similar size". Awadewit (talk) 01:57, 26 April 2009 (UTC)
• Spacings are at the same distance as the wavelength. ScienceApologist (talk) 16:09, 22 May 2009 (UTC)
• This interaction of waves to produce a resulting pattern is generally termed "interference" and can result in a variety of outcomes. - Can this be rewritten as: This interaction of waves produces a pattern termed "interference". Awadewit (talk) 01:57, 26 April 2009 (UTC)
• A color pattern formed by the interference between white light being reflected from the surface of a thin film of diesel fuel on the surface of water, and the diesel-water interface. - Is there a way to make this caption conciser? Awadewit (talk) 01:57, 26 April 2009 (UTC)
• Nonreflective coatings have an index of refraction less than the material on which they are deposited. - This seems like an awkward wording to me. What about something like this: Nonreflective coatings refract less than the materials they coat. Awadewit (talk) 01:59, 26 April 2009 (UTC)
• Normally, the lower index of refraction is not claimed to be "less refraction". I think refraction is considered binary: either you refract or you do not. I tried to adopt your wording in part, though. ScienceApologist (talk) 16:09, 22 May 2009 (UTC)
• The statement isn't true in general, anyway. Good quality AR coatings use multiple layers with different indices of refraction. The section should link to the WP articles on AR coatings and dielectric mirrors.--Srleffler (talk) 05:46, 24 May 2009 (UTC)
• Since this can only be done for one particular wavelength, usually a wavelength associated with yellow-green (λ = 550nm) where the sun is the brightest is chosen. - This is a sentence fragment. Awadewit (talk) 02:05, 26 April 2009 (UTC)
• I don't think it is, but I agree it is awkward. I removed the "yellow-green" coloring. Not necessary, IMHO, since most of the time no one can tell the color in bright light. ScienceApologist (talk) 16:09, 22 May 2009 (UTC)
• The solar spectrum does not peak at 550 nm.--Srleffler (talk) 05:46, 24 May 2009 (UTC)
• Then is this image, linked from wikipedia:Solar radiation, wrong? Coppertwig (talk) 15:26, 24 May 2009 (UTC)
• Sorry, I recalled the peak being in the infrared. The graph does seem to show it peaking nicely in the middle of the visible. Whether that is exactly at 550 nm, I can't say from that graph. I'm still not comfortable with the uncited claim that AR coatings are typically optimized based on the peak of the solar spectrum, though. If the article were going to contain that claim, I would want to see a citation to a source that says so. The luminosity function peaks at 555 nm, and is a more obvious standard for where to optimize an AR coating. --Srleffler (talk) 04:04, 28 May 2009 (UTC)
• Alternatively, if the thin-film coating has an index of refraction greater than that of the material on which it is deposited, then the reflected wave from the top of the film and the reflected wave from the film/material interface will be in phase when the film has a thickness of one-fourth of a wavelength, causing increased amplitude of reflected waves. - This sentence is a bit long. Could we break it up or shorten it? Awadewit (talk) 02:05, 26 April 2009 (UTC)
• Explaining his results by interference of the waves emanating from the two different slits, he deduced that light must propagate as waves - The first part of this sentence needs to be worded more clearly. Awadewit (talk) 02:05, 26 April 2009 (UTC)
• Augustin-Jean Fresnel did more definitive studies and calculations of diffraction, published in 1815 and 1818. - If we don't say what these studies were about, it seems rather pointless to mention them. I would suggest adding an additional phrase or deleting this material. Awadewit (talk) 02:20, 26 April 2009 (UTC)
• Refractive processes take place in the physical optics limit as a kind of scattering. - I'm not sure what "physical optics limit" means (but this might just be me). Awadewit (talk) 02:20, 26 April 2009 (UTC)
• It means where the wavelength of light is about the same size as the distances being considered. ScienceApologist (talk) 16:09, 22 May 2009 (UTC)
• It occurs in all dielectric materials - What are "dielectric materials"? Is this di-electric, signifying something about two poles or something? Awadewit (talk) 02:20, 26 April 2009 (UTC)
• A dielectic is an electric insulator. There's a wikipedia article on the subject. I'll just link to it. ScienceApologist (talk) 16:09, 22 May 2009 (UTC)
• In wavelength ranges where a medium has significant absorption, the index of refraction can increase with wavelength. This is called "anomalous dispersion" - It is best not to have one-sentence paragraphs. Awadewit (talk) 02:20, 26 April 2009 (UTC)
• Can you move the polarization diagrams to the center of the page? That would be more aesthetically pleasing. Awadewit (talk) 02:36, 26 April 2009 (UTC)
• It was this effect that provided the first discovery of polarization, by Erasmus Bartholinus in 1669. vs. It was through this effect that polarization was first discovered in 1808 by the mathematician Etienne Louis Malus. - This seems to be a contradiction. Awadewit (talk) 02:36, 26 April 2009 (UTC)

### Modern optics

• Quantum optics is not just theoretical - Is there some reason we would think it would be "just theoretical"? Awadewit (talk) 02:49, 26 April 2009 (UTC)
• Some people think quantum mechanics has no practical application! I've actually had people tell me that quantum mechanics isn't true because it is "purely theoretical". They didn't know what they were talking about, but I bet you have someone in your social circle that might believe something similar to this. ScienceApologist (talk) 16:19, 22 May 2009 (UTC)
• The section on quantum optics is quite small - I expected there to be more on this topic. Should this be expanded? When I think of "Classical mechanics" and "Quantum mechanics" in relation to physics as a whole, it would seem like there should be more on the quantum stuff than is here. But that's just my random speculation. Awadewit (talk) 02:49, 26 April 2009 (UTC)
• Not sure. Quantum optics gets pretty complicated pretty quickly. The simplest ideas are associated with photon counting: but rapidly quantum optics becomes particle physics and we begin to lose sight of the subject of the article. ScienceApologist (talk) 16:19, 22 May 2009 (UTC)
• Experiment with a laser - Not the most enlightening caption ever. Awadewit (talk) 02:49, 26 April 2009 (UTC)
• I'm wondering if the "Laser" subsection is too long compared to the rest of this section. Is the balance right? Are lasers really the most important thing in modern optics? If so, that should be made explicitly clear. Awadewit (talk) 02:49, 26 April 2009 (UTC)
• Pretty much, in my estimation. It certainly involves the most optical scientists and engineers. However, I think this is more an accident of technology and applications driving research more than anything else. It just happens to be that lasers are one of the most convenient ways to study coherent light, and that's really what you want if you are doing basic research. Not sure I can find a cite for this. ScienceApologist (talk) 16:19, 22 May 2009 (UTC)

### Everyday optics

• The optics of the human eye function when light rays pass... - "The optics...function" seems like an odd phrase to me. Awadewit (talk) 02:56, 26 April 2009 (UTC)
• The range of locations where it is possible for the eye to focus images of objects is between a far point and a near point that can be measured by seeing the range of distances from the eye where the person is able to focus and image of an object. - Can we find a less wordy way to say this? Awadewit (talk) 02:56, 26 April 2009 (UTC)
• A number of defects in vision happen as a result of optics. - This sounds very strange. What about: Defects in vision can be explained using optical principles. Awadewit (talk) 02:56, 26 April 2009 (UTC)
• Corrective lenses are measured in diopters which is the reciprocal of the focal length a positive focal length corresponding to a converging lens and a negative focal length corresponding to a diverging lens. For lenses that correct for astigmatism as well, three numbers are given: one for the spherical power, one for the cylindrical power, and one for the angle of orientation of the astigmatism. - This material seems like a tangent. Is it really necessary? Awadewit (talk) 02:56, 26 April 2009 (UTC)
• Perhaps not, but I thought it very interesting. I won't object to its removal, though. ScienceApologist (talk) 16:25, 22 May 2009 (UTC)
• Cognitive illusions include those which rely upon psychological assumptions made due to the conditions of optics. - The phrase "due to the condition of optics" reads strangely. What is it that you are precisely trying to say? Awadewit (talk) 03:04, 26 April 2009 (UTC)
• Other results from physical and geometrical optics apply to camera optics. For example, the maximum resolution capabilities of a particular camera set-up is determined by the diffraction limit associated with the pupil size and given, roughly, by the Rayleigh criterion. - This paragraph just seems tacked on to the "Photography" subsection. How necessary is it? Awadewit (talk) 03:04, 26 April 2009 (UTC)
• It connects optical principles directly to photography in a way that many photographers may not be aware of. I think it's important. Again, I won't object to its removal, but I'm not going to do it. ScienceApologist (talk) 16:25, 22 May 2009 (UTC)

## Let's get this wrapped up

This article has been forked from Wikipedia for a month and a half now. That's too long. Luckily, no significant edits have been made to the original optics article during this time, but the longer we wait the more likely this will be a problem. I'm also a bit concerned about all of the edits made to this version by Awadewit, as that will require some type of attribution when the article is copied over. Preferably, only SA should be editing this fork (so as not to create unnecessary licensing complications). I'll extend my offer of unblocking SA to make the edit for another week, but that's it. If it's not ready by then, I'm afraid you're on your own. The longer we wait, the more likely it will be that the merge will cause significant disruption (besides the banning issue). Kaldari (talk) 22:39, 28 April 2009 (UTC)

Oh, I'm sorry about that. I wasn't really thinking about attribution. I was just blissfully working on articles in my usual way. Awadewit (talk) 05:42, 30 April 2009 (UTC)
This is looking really good. Do please merge with w:optics, whoever has to make the edits. Sj (talk) 11:54, 5 May 2009 (UTC)
The actual move to Wikipedia was accomplished, for the record, with 00:18, 27 May 2009‎. There was an earlier attempt, at 15:07, 6 April 2009‎, which was reverted for procedural reasons. Before the port over to Wikipedia, there was a discussion at [5], and in ensuing talk sections. --Abd (talk) 15:51, 7 January 2014 (UTC)

Imagine my surprise when someone told me that SA was trying to write a featured article. "Never!", I thought, that dildo couldn't even spell "featured article" let alone write one. So, with these thoughts in mind, I looked with some interest at the article here to see if it was any good. It wasn't. Almost the first thing to catch my eye was the complete nonsense in the history section. Al Kindi - "the first to articulate emission theory". What complete bollocks, Plato did that almost 1000 years previously and it's unclear if he's even the first. Al Kindi did do some important work in the history of optics and did discuss emission theory, but he's not that big a name. Talking of big names, where is Euclid who set out the laws of reflection, and Ptolemy who dealt with refraction. No mention of these giants of optical history, and instead just the guff about Al Kindi. And talking of Arabs, where is Ibn al-Haytham who actually proved Plato's emission theory wrong using (wait for it) the scientific method and whose books on optics rank alongside Newton's Principia as some of the greatest in the history of physics!

Add to all this the fact the true origins of optics go back much further and start with the use of light and shadow and the development of crude mirrors rather than with the first lens and what you have is complete pile of shite for a history section. This is not even a B on the quality scale yet, let alone a featured article. Davkal (talk) 14:38, 16 May 2009 (UTC)

Thanks for the help. Your suggestions have been implemented! ScienceApologist (talk) 14:49, 22 May 2009 (UTC)
Wow, what a positive attitude, SA! I'm impressed! Davkal, I'm not sure what Wikisource's policies are, but I'm sure they would have allowed you to have just commented on the content and not on the contributor. Coppertwig (talk) 00:33, 24 May 2009 (UTC)
Of course he's on his best behaviour here. That's because he can't wait to get back to wiki and resume issuing threats of off-wiki harassment to those he can't beat by arguing, and emailing pornographic materials to opponents at their places of employment, and sending malicious complaints to opponents' employers, and all the other lovely things that made him so much fun to have around. And when that happens again, and the person has a less understanding employer and actually loses their livelihood, where will you be coppertwig that day. You'll be saying fuck all, or claiming that we don't know 100% that it's SA like all the other times he's been caught in the act of one or another outrageous abuses. Just know that your supporting a fucking psycho and stand up and be counted when the shit hits the fan.Davkal (talk) 15:24, 25 May 2009 (UTC)

## version replaced

I've replaced the version here with the one from the proper wiki. Apparently the general consensus is that the article is pretty shit and needs a considerable amount of work. Since SA is banned from the proper wiki I thought he might like to do some of the huge amount of work and will be able to do so here. Happy editing.

BTW, JVDB - "high-traffic page" lol. That'll be the three edits in two days then. What a shmendrik. Daveyboy (talk) 23:25, 31 May 2009 (UTC)

This was all fluff. This was a user space draft of an article written to be an improvement, in the opinion of the author, over the standing Wikipedia article. It should never have been subject to any editing here without the permission of the author. That's why this was in his user space, not in mainspace here, and Wikisource is not a place to draft articles; this is, if this usage was inappropriate, ScienceApologist should have been so informed, and directed to Wikiversity, where such drafting can be entirely in order, and is routinely accepted if done in user space. (It can also be done in mainspace, as an attributed exercise, but that is more complicated to preserve neutrality.) Moving the Wikipedia article version here, then, by Daveyboy, entirely missed the point. Currently, the article is blanked, which is appropriate of ScienceApologist is not going to pay attention here. However, anyone can copy this source, or the Wikipedia source, elsewhere with the proper attribution, and work on it under their own responsibility. --Abd (talk) 15:56, 7 January 2014 (UTC)

## The significance of this history

The history of this draft shows a way beyond certain severe limitations on Wikipedia. ScienceApologist was, at the time, site-banned on Wikipedia. He was nevertheless able to create an article here that most observers, including me, thought was a great improvement over the Wikipedia article. Note that I was somewhat involved in the ban of SA, having pointed out certain disruptive behavior there. The eventual port of this article was not just supported by "SA supporters."

A judgment of overall article quality is not a judgement as to every specific item,, but Wikipedia process normally focuses on each snippet of text at a time, with little regard for overall quality. The result is "design by committee," famous for producing, under some conditions, boring, uninteresting, and often confusing products.

SA demonstrated something quite different. At his own risk, he put in substantial work to create this draft. He is probably an expert in the field, and also a skilled editor. Now, consider this: suppose that this happened more often. Suppose that articles were subject to the possibility of mass change, though an RfC with a single Yes/No question: which is better, This or That? Such a discussion is not *routinely* possible, because it involves, to be functional, many editors, but *on occasion*, and especially with long-standing articles that have become impacted with the results of many conflicts, such an RfC fits within existing policy.

(In theory, each edit is to be kept if it improves the article, and rejected if it does not, but we all know how that goes!)

Something like an RfC was done, at [6]. It was enough. Opposition collapsed, and opposition based on the ban status of SA was irrelevant from the beginning. Users are banned for disruptive behavior on-wiki, not to prevent them from creating usuable and reusable content elsewhere, nor to prevent editors in good standing from using this material. It is not "meat puppetry," as has sometimes been alleged.

This same process could be followed more routinely, and Wikiversity is where this would have been fully relevant. It is not uncommon there for users to write draft Wikipedia articles. If they are in user space, I have never seen any questioned or proposed for deletion. Wikiversity is for educational materials and "learning by doing." Such draft articles can also be in mainspace, but I have avoided them being at the top level in mainspace, because that could raise neutrality issues. SA clearly, on Wikiversity, could have had totally free rein to edit the article as he saw fit, if it was in user spac. He'd have been protected in that by WV administrators. As an attributed draft in a subspace of, say, a resource on Optics, it would have been completely appropriate as well, with SA allowing or reverting changes by other editors, being allowed, as to what would effectively be an essay (or "student exercise") by him, quasi-administrative rights. (I call this "section management," where users may create sections of resources, and as long as they are not misleadingly presented -- i.e., with a pretense that they represent consensus approval, anything but the opinion or work of the author --, they do not violate neutrality policy.)

Because Wikiversity allows original research, and the expression of user opinion, and doesn't allow mainspace resources that are simply copies or versions of Wikipedia articles (such are often deleted), I have suggested and practiced, without opposition, that draft Wikipedia articles be presented in subspace as student exercises in writing Wikipedia articles.

There is thus a way for editors banned on Wikipedia to still create material that could be useful on Wikipedia. SA's work demonstrated the possibility. It worked. --Abd (talk) 16:21, 7 January 2014 (UTC)