LIGHT AND THE QUANTUM 



119 



on the surface of a liquid they meet to form a 

 beautiful pattern, such as you must frequently 

 have observed, and in which the ripples from 

 the two sources alternately offset and augment 



Figure 22 

 Fresnel Mirrors 



one another. Such a pattern may be represented 

 diagrammatically, as in Figure 21, by drawing 

 a series of concentric circles about two distinct 

 centers. So if a beam of light is divided, and the 

 two parts are allowed to converge once more, 

 they produce a quite similar interference pat- 

 tern. 



Figure 22 represents one of the simplest con- 



