(a) How does an unpolarized light incident on polaroid get polarized ?
Describe briefly, with the help of necessary diagram, the polarization of light by reflection from a transparent medium. (b) Two polaroids 'A' and 'B' are kept in crossed position. How should a third polaroid 'C' be placed between them so that the inlensity of polarized light transmitted by polaroid B reduces to `1//8^(th)` of the intensity of unpolarized incident on A?

Explanation

(a) When the light waves transmit only one component parallel to a special axis, then the resulting light is called lineraly polarised or plane polarised. Since sound waves are longitudinal waves and polarisation of the waves can only be exhibited by the transverse waves.
(b) A polaroid consists a material Tourmaline, which polarises light.
If an unpolarised light wave is incident on such a polaroid, then the light wave get linearly polarises with the electric vector oscillating along a direction perpendicular to the aligned molecules.