98 



A HALF-HOUR WITH 



An imaginary section of a beam 

 of common light is usually repre- 

 sented thus : J 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. 



&, bundle of plates of thin glass ; b, ray of ordinary light ; 

 ft, ray polarized by reflection; d, ray polarized by refraction. 



A polarized ray may be obtained by reflection 



