Question

State Brewster's law of polarisation of light. The polarising angle for a transparent medium is ${60}^o$. What will be the refractive index and angle of refraction of the medium?
$\tan {60}^o=\sqrt{3}$

Answer 1

Brewster’s law is a relationship of light waves at the maximum polarization of a light.

The law states that the p-polarized rays vanish completely on different glasses at a particular angle. Further, the polarization angle is also called as Brewster’s angle. It is an angle of incidence where the ray of light having a p-polarization transmitted through a dielectric surface that is transparent without any reflection. While, the unpolarized light at this angle is transmitted, the light is reflected from the surface.

Brewster was able to determine that the refractive index of the medium is numerically equal to the tangent angle of polarization.$tan\left(i\right)=\mu$

$\therefore$ Refractive index $=\mu =tan{60}^o=\sqrt{3}$

But, $\mu =\frac{sin\left(i\right)}{sin\left(r\right)}$ by Snell's law

$\therefore r=si{n}^{-1}\left(\frac{sin{60}^o}{\sqrt{3}}\right)$

$\therefore$ Angle of refraction $=r={30}^o$