98 



A HALF-HOUR WITH 



An imaginary section of a beam 

 of common light is usually repre- 

 sented thus : 1 and, of a beam 



of polarized light 



In the following or 



diagrams we shall represent the ordinary beam 

 by three, the ordinary polarized ray by two 

 parallel lines, and the extraordinary polarized ray 

 by a single line. 



If a ray of light (Fig. 16) b impinges on a bundle 

 of glass plates, a, placed at the polarizing angle of 

 glass (56 45') the ray is in part reflected and in 

 part transmitted, and both become polarized ; c is 

 termed the ordinary, and d the extraordinary ray. 



Fig. 16. 



a, bundle of plates of thin glass ; 6, ray of ordinary light ; 

 c, ray polarized by reflection ; d t ray polarized by refraction. 



A. polarized ray may be obtained by reflection 



