D O C U M E N T 2 2 3 E X P E R I M E N T O N R A D I AT I O N 2 3 3 The light of a quasi-monochromatic source of light L falls onto a slide gate S that is alternately open during the time τ, then during the subsequent span of time τ is closed (etc.). There then develops an intermittent train of waves in the way indicated in the figure cτ is the length of a partial train of waves as well as of the subsequent gap. If the thus formed train of waves is then examined by means of a Michelson interferometer for various differences in path, classical optics then de- mands the following: Interference fringes must arise if the difference in the course of both partial beams is an even multiple of cτ they must vanish for path differences that are an odd multiple of cτ If the conception of the classical theory of light emission is essentially right, then a train of waves of the kind indicated above is produced in the arrangement in the accompanying sketch by the radiation of one atom of a canal ray. Of the single atom of a canal ray beam moving at velocity v in the direction of the arrow a sharp image is formed on the plane of a wire grating by the lens G, the wires and intervals of which are about 1/10 mm in thickness. Behind the grating, the light emerging through the grating is made parallel by another lens and thereupon interferometri- cally examined. Then, according to classical optics, the above indicated behavior of the interferences should become manifest, dependent on the difference in the path.[3] In order for this experiment to be conclusive it is necessary that the images of all the canal ray particles be formed precisely enough in the wire grating’s plane and that the image width not exceed 1/10 mm. If one denotes the thickness of the emitting atom wire grating