CBSE Class 12-science Answered

In unpolarised light, the vibrations are symmetric about the direction of propagation.For an unpolarised wave the displacement will be randomly changing with time though it will always be perpendicular to the direction of propagation.

When unpolarised light is incident on the boundary between two transparent media, the reflected light is polarised with its electric vector perpendicular to the plane of incidence when the refracted and reflected rays make a right angle with each other.

Thus when reflected wave is perpendicular to the refracted wave, the reflected wave is a totally polarised wave. The angle of incidence in this case is called Brewster's angle and is denoted by i_B. We can see that i_B is related to the refractive index of the denser medium.

Since we have i_B + r = /2 , we get from Snell's law