Q. The critical angle of the medium with respect to vacuum is $30{^\circ}.$ If the velocity of light in vacuum is $3 \times 10^{8}\ ms\ \bar{}¹,$ the velocity of light in medium is
A) $2 \times 10⁸\ ms\ \bar{}¹$
B) $1.5 \times 10⁸\ ms\ \bar{}¹$
C) $3 \times 10⁸\ ms\ \bar{}¹$
D) $\sqrt{2} \times 10⁸\ ms\ \bar{}¹$
Explanation
(b) Refractive index, $\mu = \frac{1}{\sin C}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \mu = \frac{c}{v}$
$\therefore\frac{c}{v} = \frac{1}{\sin C}$
$\Rightarrow \ \ \frac{3 \times 10^{8}}{v} = \frac{1}{\sin{30{^\circ}}}$
$v = 1.5 \times 10^{8}\ ms^{- 1}\ $
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.