358 F. E. Wright — Measurement of Extinction Angles. 



Fig. 2. 



(JU 



% 



80 

 70 



to 



50 

 40 

 30 

 20 

 10 



^ 



x 





/ 





\ 













\ 



/• 

















\ 



/ 







\ 



















A 













\ 







\ 



V 













/ 





\ 



\ 











/ 



/ 





\A \ 



\ 



\. 











f 







^ X 



\\ 









// 





/ 







"^ 



\\ 





^ 



yy 





TV 









x\ 









1 



0° 2 



.0° t 



0° 4 



0" 5 



(T fc 



0° 7 



0" g 



0° ^ 



o ( 



Fig. 2. — Curves showing relative intensity of light emerging from upper 

 nicol after transmission through polarizer, crystal plate and analyzer, the 

 positions of the crystal plate and also the analyzer ranging from 0°-90°. 

 The abscissa values refer to angular distances of the major ellipsoidal axis of 

 the crystal plate and also of the plane of the analyzer. For curves I-IV, the 



nicols are considered crossed (<p= — ) and the crystal plate alone to be 



a 



2tt 



revolved from 0° to 90°. In curve 1, sin' 2 — d (y 1 — «') = K 



1 : in curve II, 



K = 1/2 ; in curve III. K = 1/4 ; in curve IV, K = 0. Curve V shows the 

 relative intensity of the emerging light for different positions of the analyzer 

 alone (0=0, <p ranging from 0° to 90°). Curves calculated from the general 

 formula 



I 1= l/2(l+(l-K)cos20 + Kcos2(0-20)). 



