Polarization

Polarization is the action of restricting the vibrations of a transverse wave, especially light, wholly or partially to one direction.

Polarization by the reflection of light:

Brewster's Law

It states that the refractive index of a medium is numerically equal to the tangent of a polarising angle. i.e. μ=tanθp

Verification

When the incident ray falls in the junction of air and glass  then the reflected rays are partially polarized and the refracted rays are unpolarized. As the incidence angle is increased up to θp then reflected ray becomes fully polarized ( but not refracted). It (θp) is known as Brewster's angle.

Here,

θp+90°+r=180°

Or, θp+r=90°

Or, r=90°-θp

Since,

µ=sini/sinr

Or, µ=sinθp/sin(90°-θp)

Or, µ=sinθp/cosθp

Or,  μ=tanθp

Hence, Brewster's Law is verified.

Note: in the figure θB = θp of derivation