A HALF-HOUR WITH 



An imaginary section of a beam 

 of common light is usually repre- 

 sented thus : 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 j c is 

 termed the ordinary, and d the extraordinary ray. 



Fig. 16. 



a, bundle of plates of thin glass ; 5, ray of ordinary light ; 

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



A polarized ray may be obtained by reflection 



