Q.If the polarising angle for a given medium is 60°, then the refractive index of the medium is ______ (A) $\dfrac{1}{\sqrt3}$
(B) $\sqrt{\dfrac{3}{2}}$
(C) $1$
(D) $\sqrt3$

Brewster's law states $\tan\theta_p = \mu$; since $1.732 = \sqrt3 = \tan60°$, the polarising angle is $60°$.

By Brewster's law, the polarising angle $\theta_p$ for a given refractive index $\mu$ satisfies

$\tan\theta_p = \mu.$ …

By Brewster's law, the refractive index equals the tangent of the polarising angle.

By Brewster's law, when unpolarised light is incident on a transparent medium at the polarising angle $\theta_p$ (also called Brewster's angle), the reflected light is completely plane-polarised, and the refractive index of the medium is related …