POLARIZED LIGHT. |01 



me that it is not to be detected bv the unassistod 



Fig. 18. 



a, plate of tourmaline ; 6, ray of common light j c, raj 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 96) 

 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 ; but if we 

 gradually revolve it until it stands at right angles 



L 



Of 



L J 



Pig. 19. 



a a', two slices of tourmaline with angles coincident 

 b, beam of common light ; c, polarized ray ; fc, ditto trans- 

 mitted. 



to the polarized, the ray is intercepted and de- 

 stroyed. 



