Question

An unpolarized light is incident on the boundary between two transparent media.State the condition when the reflected wave is completely plane polarized.Find out an expression for the angle of incidendr

Answer 1

The reflected wave will totally polarised if reflected wave and refracted wave are perpendicular to each other.

Let us consider that incident angle is $i_p$ and refracted angle is r.

from figure,

$\quad i_p+90^{\circ}+r=180^{\circ}$

$\implies r=90^{\circ}-i_p$......(1)

according to Snell's law,

$1sini_p=\mu sinr\\\\\mu=\frac{sini_p}{sinr}$

from equations (1),

$\mu=\frac{sini_p}{sin(90^{\circ}-i_p)}$

$\boxed{\bf{\mu=\frac{sini_p}{cosi_p}=tani_p}}$

here, $\mu$ refractive index of transparent medium. above expression is known as Brewster's law and $i_p$ is known as Brewster's angle.