Question

For the same angle of incidence, the angles of refraction in media $P, Q$ and $R$ are $35^{\circ}, 25^{\circ}$ and $15^{\circ}$, respectively. Which of the following relation hold true for the velocity of light in medium $P, Q$ and $R$ ?

• A. $v_{P}< v_{Q}< v_{R}$
• B. $v_{P}< v_{R}< v_{Q}$
• C. $v_{P} >v_{Q} >v_{R}$
• D. $v_{P} >v_{R} >v_{Q}$

Answer 1

Answer: (C)

For same angle of incidence, the angle of refraction is minimum in medium $R$

As, $\mu=\frac{\sin i}{\sin r}$
or $\mu \propto \frac{1}{\sin r}$
$\Rightarrow \mu$ is maximum for $R$,
since $r$ is minimum and hence, $\sin r$ is minimum.
Also, $\mu=\frac{c}{v}$
Therefore, if $\mu$ is maximum, $v$ is minimum
i.e., velocity of light is minimum in medium $R$ and order of velocity will be
$v_{P} >v_{O} >v_{R}$