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



Fig. 3. 



Fig. 3. — Intensity curves for crystal plates making angles 0', 5', 10', 15', 

 20', 25', 30', 40', 45', 50' and 1° with plane of polarizer. Analyzer revolved 

 about axis from 88° to 92° with lower nicol plane. 



• -2 *™ / / 



■ a')=K=l 



Curves calculated from the formula 



1=1/2(1 4- cos 2 (<p 



'•&))• 



The 



