"N" Rays/On Peculiarities Presented by the Action Which "N" Rays Exercise upon a Dimly Lighted Surface

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On Peculiarities presented by the Action exercised by "N" Rays on a Dimly Lighted Surface (February 2, 1904).

Consider a phosphorescent screen, or, more generally, a dimly lighted surface. If this surface is viewed normally, one notices that the action of "N" rays is to render it more luminous; if, on the contrary, the surface is viewed very obliquely, nearly tangentially, the action of "N" rays is to render it less luminous. In other words, the action of "N" rays increases the quantity of light normally emitted, while it diminishes the light emitted in a very oblique direction. If one looks at it in an intermediate position, no appreciable effect is observed. This explains the fact, observed in all "N" ray experiments, that only the observer placed exactly in front of the sensitive screen perceives the effect of these rays. It also shows how illusory it would be to try to make an audience witness these experiments: the effects perceived by different persons, depending as they do on their positions with regard to the screen, would certainly be contradictory or imperceptible. The rays I have called N1 rays have an inverse action in all cases to that of "N" rays; they diminish the light emitted normally, and increase the light emitted tangentially. M. Macé de Lepinay (see C. R. t. cxxxviii. p. 77, January 11, 1902) has found that sound vibrations increase the glow of a phosphorescent screen as seen by an observer viewing it normally. I have noticed that if the screen is viewed tangentially, the phosphorescence is seen to decrease under the action of the sound-waves. The action of a magnetic field or of an electromotive force on a feebly luminous surface, discovered by M. C. Gutton (see C. R. t. cxxxviii. p. 268, February 1, 1904), presents the same particularities.

To sum up, in all the above-mentioned actions, the modification undergone by the luminous emission consist in a change in its distribution along the different directions comprised between the normal and the tangent plane to the luminous surface.