Nicol prism is a type of polarizer, an optical device used to generate a beam of polarized light.
When unpolarized light enters into nicol prism, it splits into two plane polarized rays. This is known as double refraction of the two ray (O and E) one ray which has vibrations perpendicular to the principal axis is absorbed and the ray which has vibrations parallel to the principal axis comes out as plane polarised. This property is called dichroism.
