Poynting[1] to the emission of a moving surface. The mentioned authors confine themselves, however, to the case of perpendicular incidence or emission. Incidentally, Poynting[1] has calculated by a different method the radiation pressure at perpendicular emission with the same result.
If we insert values (26) into (16), then we obtain the pressure upon the surfaces and . For example, if we calculate the pressure acting upon surface , and express this value for example by the density of the total incident radiation
,
then we obtain
(27) |
which of course is in agreement with the corresponding one of Abraham.[2]
The pressure upon a moving mirror incidentally can be derived very easily from the mentioned hypothesis, and one also obtains the law of reflection with one stroke.[3] It follows indeed immediately from it, that the intensities of the incident and reflected light behaves inversely as the wavelengths, and directly as the oscillation numbers.[4]
§ 5.
Now we want to concern ourselves with the fraction of the energy in , which is due to the apparent radiation and which is gained from mechanical work. If we set into (19) the values from (26) for and , it becomes
We put
(28) |