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 3 not know but he certainly did not lie. There cannot be any question of a genuine denial [11] at most one could say that it is objectionable to reproduce private con- versations in the press without authorization. Best would be, however, to say noth- ing at all, because one would thus at most stir up the issue again. Paper is forbearing and the newspaper reader forgetful—in a couple of years we shall all be dead and the new generation will fret over and amuse themselves again with new follies. I send you the article back in the same post. P.S. An honest person should be respected, even if he holds and defends different views from one’s own.[12] 42. From Gregory Breit[1] Leyden, 31 January 1922 [Not selected for translation.] 43. “On the Theory of Light Propagation in Dispersive Media” [Einstein 1922f] Submitted 2 February 1922 Published 27 February 1922 In: Preußische Akademie der Wissenschaften (Berlin). Physikalisch-mathematische Klasse. Sitzungsberichte (1922): 18–22. In a notice that just recently appeared in these Berichte,[1] I proposed an optical ex- periment for which, based on my reflections, the undulatory theory would lead one to expect results that are at odds with the quantum theory. The reasoning was as fol- lows. A canal-ray particle moving within the focal plane of a lens generates light with eccentric surfaces of equal phase that by the lens’s diffraction are transformed into nonparallel planes (a “fanned out” system of planes). In such light the frequen- cy, hence also the propagation velocity, is a function of location. If one lets such a [p. 18]