196 ELLIPTIC POLARIZATION. 



Now a denoting this azimuth, the amplitudes of the two compo- 

 nents are cos a and sin a, that of the original vibration being 

 unity ; so that if v and v', denote (as before) the ratios of the 

 amplitudes of the reflected and incident vibrations in the two 

 principal planes, the amplitudes of the two components in 

 the reflected ray will be v cos a, and v' sin a. These will be 

 equal, and therefore the reflected light circularly-polarized, 

 when 



v cos (i - r) 

 tan a = -, 



v ooa(*+r) 



If the principal incidence were the same as the angle 

 given by Brewster's law, cos (i + r) = 0, and a = 90. But 

 this not being the case, cos (i + r) is not actually evanescent ; 

 and the azimuth, a, at which the light is circularly-polarized, 

 is a few degrees less than 90. 



