D O C U M E N T 4 3 L I G H T I N D I S P E R S I V E M E D I A 6 7 , therefore must be set, so[9] . Condition (3) here yields . (6) We now ask: What will happen to the group of waves[10] that passes the plane at the short interval at ? As is known, such a group propagates not at the velocity but at the group velocity . For the starting points illuminated by this group, the relation must be satisfied.[11] Equation (6) thus yields also in this case . (7) Therefore the group of waves propagates rectilinearly along the y-axis and the wavelength standard has the same direction. Thus is shown that light generated by canal-ray particles moving within disper- sive media does not experience deflection—in contradiction to the above elemen- tary consideration. This is also the outcome of the experiment that was performed by Messrs. Geiger and Bothe at the Physikalisch-Technische Reichsanstalt through E. Warburg’s[12] kind arrangement. Based on this finding of the theoretical consid- eration, more profound conclusions about the nature of the elementary process of emission cannot be drawn from this experiment. It should also be noted that a deflection of light in dispersive media dependent on the state of motion of the emitting molecule would lead to a contradiction with the Second Law of Thermodynamics, as Mr. Laue pointed out to me. Because such a bending is not to be expected by undulatory theory either, however, it is probably not necessary to demonstrate this point more precisely. I am pleasantly obliged to express my cordial thanks here also to Messrs. War- burg, Geiger, and Bothe. n n0 dn ------ -dω + n0 dn ------ -γξ + = = 1 V --- 1 c -- - n0 dn ------ -γξ + = H ω0 γξ) + ( t 1 c -- - r0 x r0 ----ξ n0 dn ------ -γξ + α + = γ t r0 c ---- n0 ω------ dn - + ω0 c ------n0---- x r0 + 0 = y 0= t 0= V c m --- -= Vg c n ω------- dn + --------------------- = t r0 Vg ----- -– t r0 c ---- n ω------ dn - + 0 = = x 0= [p. 22]
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