POLARIZED LIGHT. 



101 



me that it is not to be detected bv the unassisted 

 eye] 



Fig., 18. 



a, plate of tourmaline ; &, ray of common light ; c, ray of 

 polarized light. 



In order to distinguish the difference between 

 ordinary light and that which has become polar- 

 ized, special means are required for that purpose. 

 It is an axiom that the medium capable of pro- 

 ducing polarized light is also capable of analyzing 

 it. Thus, if the reflected ray c (Fig. 16, page 9G) 

 is reflected on a mirror whose surface coincides 

 with that of the polarizer, the ray will be reflected 

 in the same manner as an ordinary ray j but if we 

 gradually revolve it until it stands at right angles 



CL 



of 



d 



Fig. 19. 



a a, two slices of tourmaline -with angles coincident ; 

 I, beam of common light ; c, polarized ray ; d, ditto trans- 

 mitted. 



to the polarized, the ray is intercepted and de- 

 stroyed. 



