Test of a theory of radiation

Abstract

It is well known that the energy of the electrons ejected from matter by radiation is much greater than could have been given by the radiation to the atom containing the electron on the classical theory of electrodynamics, the discrepancy being especially marked in the case of radiation of high frequency, such as X-rays and γ -rays. To account for this it has sometimes been supposed that the energy in a wave of radiation is not continuously distribute but concentrated in certain small regions. One particular form of this hypothesis has recently been used by Silberstein in forming a theory of the action of the photographic plate. This regards the energy as concentrated in a few rays, to use the language of geometrical optics, to which Silberstein has given the name of “light darts.” It has occurred to the author that the rapid motion of the atoms emitting light in the positive rays affords a means of testing this hypothesis. Suppose that light from a moving source is made to traverse two slits as in fig. 1. Ignoring diffraction effects, which for the dimensions of the apparatus actually used are inappreciable, only light emitted from that portion of the path of the moving particle which lies between the dotted lines in fig. 1 can get through the slits. If, therefore, the emitting particle is moving so fast that it traverses this portion of its path in less time than it takes to emit a complete “light dart,” during some portion at least of the emission the light from the particle will be unable to get through the slit. Thus all the “light darts” will arrive in fragments. Without further elaboration of the hypothesis it would be impossible to say what the Effect of these fragmentary “light darts” would be. They might be supposed to act like radiation of proportionally less frequency, or they might be supposed to have no effect until joined by another fragment, but if we are to adhere to the idea of the energy being distributed along the length of the light dart they cannot produce the normal effect of radiation of their own frequency.