Question

Refraction of light from air to glass and from air to water are shown in figure (i) and figure (ii) below. The value of the angle $\theta$ in the case of refraction as shown in figure (iii) will be

• A. $30^{\circ }$
• B. $35^{\circ }$
• C. $60^{\circ }$
• D. $41^{\circ }$

Answer 1

Answer: (B)

Using Snells law,
${}^a{\mu }_g=\frac{sin60^{\circ }}{sin35^{\circ }},{}^a{\mu }_w=\frac{sin60^{\circ }}{sin41^{\circ }}$
and ${}^w{\mu }_g=\frac{sin41^{\circ }}{sin\theta }$
${}^a{\mu }_w{\times }^w{\mu }_g={}^a{\mu }_g$
$\Rightarrow \frac{sin60^{\circ }}{sin41^{\circ }}\times \frac{sin41^{\circ }}{sin\theta }=\frac{sin60^{\circ }}{sin35^{\circ }}$
$\Rightarrow sin\theta =sin35^{\circ }$ or
$\theta =35^{\circ }$