(b) as shown in the following figure, the transmitted ray p'q' entering the gypsum crystal makes an incident angle of 40" and the refracted ray q'r makes an ang

(b) As shown in the following figure, the transmitted ray P'Q' entering the gypsum crystal makes an incident angle of 40" and the refracted ray Q'R makes an angle of 25 with the normal. Gypsum a' i) Determine the 2V optic angle : ii) Determine the apparent optic angle 2E: