Question

When the angle of incidence on a material is ${60}^{\circ }$, the reflected light is completely polarized. The velocity of the refracted ray inside the material is $(\text{in m/s}$)

• A. $3\times {10}^8$
• B. $\frac{3}{\sqrt{2}}\times {10}^8$
• C. $\sqrt{3}\times {10}^8$
• D. $0.5\times {10}^8$

Answer 1

The correct option is C $\sqrt{3}\times {10}^8$

Given
Polarizing angle, $i_p={60}^{\circ }$

When an unpolarized light is incident at polarizing angle $\left(i_p\right)$ on a transparent medium of refractive index $\mu$ then the reflected light is completely polarized and from Brewster's law,

$\mu =\tan i_p=\tan \left({60}^{\circ }\right)=\sqrt{3}$

From the definition of refractive index
$\mu =\frac{c}{v}$

$\Rightarrow \sqrt{3}=\frac{3\times {10}^8}{v}$

$\therefore v=\sqrt{3}\times {10}^8\text{m/s}$

Hence, option $\left(\text{C}\right)$ is correct.