Question

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

• A. $P$
• B. $Q$
• C. $R$
• D. $S$

Answer 1

Answer: (D)

The speed of light reduces when it travels from rarer to denser medium.
When light travels from rarer to denser medium, it bends towards the normal.
Thus, speed of light is minimum when it bends maximum towards the normal for same angle of incidence, i.e. angle of refraction is least.
So, angle of refraction is least, i.e. $20^{\circ}$ in medium $S$