2 9 6 D O C . 2 7 8 I N T E R F E R E N C E O F C A N A L R A Y L I G H T that the field that determines the interference cannot be generated by an instanta- neous process as is suggested by the quantum theory rather, it seems the wave theory retains full validity for the generation of the interference field, in accordance with the interpretation by Bohr and Heisenberg.1) [9] Case 3. A slit or grating is interposed between the canal ray and interference ap- paratus. Let l be calculated as positive if the mirror S1 is farther away than mirror S2.[10] It was the case that the canal rays pass by behind a slit of the width b that first turned my attention to the problem treated here.[12] Imagine a canal ray parti- cle that goes by slit b di- rectly behind the screen S. The time of the passing by is , the length of the train of waves sent through the screen ac- cording to the wave theo- ry is equal to . If the interference apparatus generates a difference in path d, which is equal to or greater than , then no interference ought to be perceptible. I doubted the correctness of this consequence, however, because owing to the facts of quantum theory I suspected that the light sent out by the canal rays by elemen- tary emissions in a definite direction was strictly monochromatic.[13] I believed that the fact that the elementary act of emission occured in slit b could not be crucial to the composition of the emitted light, because I believed that the generation of the wave field should also be attributed to an instantaneous act. That this does not agree with the basic assumption of this paper was demonstrated earlier by case 2. It will be proven even more distinctly here. We ask about the composition of radiation that arrives from an infinitely distant point on the axis, in dependence on the path difference d. For this purpose, we again imagine the canal ray shifted into infinity and substituted by light sources at rest of 1) In particular, it is not permissible to assume that the quantum process of emission, which is en- ergetically defined by position, time, direction, and energy, is defined by these quantities also in its geometrical characteristics. The correctness of the interpretation by Bohr, Kramers, and Slater hence seems merely to constitute these authors’ willingness to abandon the rigid validity of the conservation laws.[11] [p. 338] b v -- - b-- c v b c v --