LIGHT AND THE QUANTUM 123 



either mirror regardless of the presence of the 

 other mirror; the phenomenon of interference 

 would not exist. It therefore seems necessary to 

 return to the original idea of Newton that light 

 has two aspects. Recognizing that the energy 

 goes out in corpuscles, we must assume some- 

 thing else, something, indeed, which obeys the 

 laws of wave motion, to determine where these 

 corpuscles shall go. This something we may call 

 the interference field, and it may be that we 

 shall conclude that this field is present even at 

 times when there is no actual emission of energy. 

 Tliis is a view which has been advanced by 

 Slater^ and by Swann,^ and the resolution of 

 the phenomenon of light into its two aspects, 

 one of which concerns the establishment of an 

 interference field, and the other the actual 

 transfer of energy, not only promises to be ex- 

 tremely useful, but I think it will prove neces- 

 sary. But the particular way in which these two 

 authors assume the light corpuscles to be di- 

 rected by the field presents such difficulties that 

 we are left with the feeling that the paradox of 

 quantum theory is only partially resolved. If I 

 now devote the remainder of this chapter to an 



2 Slater, Nature, 113, 307 (1924). 

 aSwann, Science, 61, 425 (1925). 



