To avoid double refraction of light propagating inside a uni

To avoid double refraction of light propagating inside a uniaxial crystal (in which O- and E-waves travel along the same direction with the same velocity), the angle theta between the light ray and optical axis of the ciystal must be A. theta = 0degree (Parallel), B. theta = 90degree (Perpendicular), C. theta = plusminus 45degree, D. theta = 0degree or theta = 90degree depending on uniaxial positive or negative crystal.

Solution

answer is A that is the angle between light ray and optical ray must be parllel to each other to avoid double refraction especially in calcium crystals (uniaxial crystal)