Brewster's Law of refractive index

Class : XII - Physics  

 

Polarization by Reflection :-

When an unpolarized light is incident on a transparent surfaces like water, glass etc. the reflected and refracted rays are partially polarized.

Brewster's Law :-

Statement :-

The tangent of the polarizing angle (Ѳ_p) is equal to the refractive index of the material.

Theory :-

When the angle of incidence of the unpolarized light on a transparent surface is gradually increased , a time comes when the reflected rays are completely polarized. and the corresponding angle at which the reflected rays are plane polarized is knownas polarizing angle (Ѳ_p), it is also known as Brewster's angle.

If the angle of incidence be 'i' , angle of refraction be 'r' and when light reflected becomes plane polarized the angle of incidence will be equal to (Ѳ_p) i.e. polarizing angle. Then,

(Ѳ_p) + 90⁰ + r         =             180⁰     [Here, (Ѳ_p) is the angle of incidence ]

r                              =             90⁰ - (Ѳ_p) ……. (i)

 In this way, Brewster's law can be verified experimentally.