Question

Distinguish between unpolarized light and linearly polarized light. How does one get linearly polarised light with the help of a polaroid?

Answer 1

Unpolarised light: A light wave in which electric vector oscillates in all possible directions in a plane perpendicular to the direction of propagation is called unpolarised light as shown in the fig(i).

Linearly polarised: if the electric vector's vibration is restricted to one direction only in a plane perpendicular to the direction of propagation. the light is called linearly polarised. As shown in the fig(ii):

Polaroid is a special crystalline solid which contains a special axis called optic axis. When we make a unpolarised light to fall on a polaroid, only vibration parallel to optic axis is allowed to pass through and all other vibration are cut. Thus, the output is a plane polarised light.As shown in the fig(iii).