Question

For the same angle of incidence, the angles of refractive in media '$P$', '$Q$', '$R$' and '$S$' are ${50}^o,{40}^o,{30}^o,{20}^o$ respectively. The speed of light is minimum in medium

• A. $P$
• B. $Q$
• C. $R$
• D. $S$

Answer 1

The correct option is D $S$

Let the speed of light in medium be $v$ and that in rarer medium be $c$.

Using $v\sin i=c\sin r$

We get $v=\frac{c\sin r}{\sin i}$

$⟹$ $v\propto \sin r$

As sine is an increasing function, thus $\sin r$ increases with increase in $r$.

Thus speed of light is minimum in the medium having lowest refractive angle i.e. $S$