In double refraction, the stationary image can be produced by:
A) O-Ray
B) E- ray
C) Both O- ray and E- ray combined together
D) Sometimes O- Ray sometimes E-ray

Hint: Double refraction happens due to the difference in the refractive index of a medium. In double refraction, a single ray of an unpolarised medium is split into two after entering an anisotropic medium. The two types of rays in double refraction are the Ordinary ray denoted by O-Ray and the extraordinary ray which is denoted by E-ray. The extraordinary rays are affected by the medium while the ordinary rays are unaffected by the medium.

Complete step by step solution:
Double refraction is an optical phenomenon where a single ray of unpolarized light will enter an anisotropic medium and will be split into two rays. Both rays will travel in different directions. One ray will be refracted after passing through the medium, this ray is called the extraordinary ray. The other ray will not be affected by the medium and is called the ordinary ray.

The ordinary ray has a constant refractive index in all directions. The extraordinary ray has components both parallel and perpendicular to the optical axis of the crystal, hence its refractive index varies in different directions.

Since the ordinary ray has a constant refractive index in all directions, stationary images can be produced by ordinary rays. Due to the variation in refractive indices, extraordinary rays cannot produce stationary images

Therefore the answer is the ordinary ray. Hence the correct option is (A), O-ray.

Note: Birefringence is the optical property responsible for the double refraction. This is the difference in the refractive index of the material. Both the extraordinary rays and the ordinary rays will be polarised in planes vibrating at right angles with each other. If the incident light falls on the crystal through its optical axis then it will not split into two.