Question

Write definitions of plane of vibration and plane of polarization. Explain the working process to obtain plane polarized light by Nicole Prism. Draw necessary diagram.

Answer 1

Plane of vibration : The plane in which the vibration of electric field and magnetic field vibrate it is always perpendicular plane with direction of propagation.

Plane of polarisation : The plane in which remaining vibration vibrate after the process of polarisation. It is also perpendicular plane to the direction of propagation of light.

POLARISATION BY NICOLE PRISM :-

Principle : When a thin film of canada balsam is placed between two calcite pieces, the 0-rays of the unpolarised incident light get eliminated through the phenomenon of total internal reflection while E-rays are transmitted unaffected and emerge as a beam of plane polarised light.

Working : The principal section ACGE of a Nicole prism. The diagonal AG represents the canada balsam layer. When ray of unpolarised light passes from a portion of the calcite crystal into the layer of canada balsam, it passes from a denser to a rarer medium. When the angle of incidence is greater than the critical angle $(\simeq {69}^{\circ })$, the ray is totally reflected and absorbed by a blackened surface. The E-ray is not effected because it is travelling from rarer medium to denser medium. It gets transmitted through the Nicole prism. Hence a ray passes from Nicole prism get polarised.