Discuss about Nicol prism.

Explanation

Nicol prism is an optical device incorporated in optical instruments both for producing and analysing plane polarised light. The constructin of a Nicol prism is based on the phenomemon of Double refraction.
One of the most common forms of the Nicol prism is made by taking a calcite crystal which is a double refracting crystan with its lenght three times its breadth. It is cut into two halves along the diagonal so that their face angles are `72^(@) and 108^(@)`. Two two halves are joined together by a layer of canada balsam, a transparent cement.