(a) How does one demonstrate, using a suitable diagram, that unpolarized light when passed through a Polaroid gets polarized?

(b) A beam of unpolarized light is incident on a glass-air interface. Show, using a suitable ray diagram, that light reflected from the interface is totally polarized, when μ = tan i_B, where μ is the refractive index of glass with respect to air and i_B is the Brewster's angle. 

Polarization of light is referred to as restricting the vibration of light in a perpendicular direction perpendicular to the direction of propagation of wave.

The vibration of particles of light which is parallel to the axis of crystal passes through the Polaroid on passing an unpolarized light. All other vibrations are absorbed and that is why intensity of emerging light is reduced.

The plane of vibration here is ABCD, in which the vibrations of the polarized light is confined and the plane KLMN is called plane of polarization. KLMN is perpendicular to the plane of vibration.

Reflected light is totally polarized, when unpolarized light is incident on the glass-air interface at the Brewster angle i_B. This is known as Brewster’s law.

The reflected component OB and refracted component OC are mutually perpendicular to each other, when light is incident at Brewster’s angle.

Now, using Snell’s law, we have

i = i_B and r = (90⁰ – i_B)

Therefore,