Question

A wave has velocity $v$ in medium $P$ and velocity $2v$ in medium $Q$. If the wave is incident in medium $P$ at an angle of ${30}^{\circ }$ then the angle of refraction will be

• A. ${30}^{\circ }$
• B. ${45}^{\circ }$
• C. ${60}^{\circ }$
• D. ${90}^{\circ }$

Answer 1

The correct option is D ${90}^{\circ }$

$v=\frac{\sin i}{\sin r}=\frac{v_1}{v_2}$
$\Rightarrow \sin r=\sin {30}^{\circ }\times \frac{2v}{v}$
$\Rightarrow \sin r=\frac{1}{2}\times 2\times 1$
$\Rightarrow r={90}^{\circ }$.