Question

Show that reflected and refracted beams are mutually perpendicular when the angle of incidence is equal to polarizing angle.

Answer 1

If n be the refractive index of transparent medium and $i_P$ the polarising angle,

then according to Brewster

n = tan $i_P$

It is called Brewster’s law and angle of incidence $i_P$ is also called Brewster’s angle.

The value of Brewster’s angle for glass is ${57}^0$ and for water it is ${53}^0$.

At polarising angle the reflected and refracted rays are mutually perpendicular.

To prove it let polarising angle be $i_P$,

angle of reflection r′ = $i_P$ and angle of refraction be r

Comparing (1) and (2), we get

.e., at polarising angle of incidence,

the reflected and refracted rays are mutually perpendicular.