Question

If the angle of incidence in denser median is equal to the critical angle, then the angle of refraction will be:

• A. $0^{\circ }$
• B. ${45}^{\circ }$
• C. ${90}^{\circ }$
• D. ${180}^{\circ }$

Answer 1

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

Critical angle is defined as $\sin {\theta }_c=\frac{n_1}{n_2}$
Given : $i={\theta }_c$
$⟹\sin i=\sin {\theta }_c=\frac{n_1}{n_2}$
Using Snell's law of refraction :
$n_1\times \sin r=n_2\sin i$
$\therefore$ $n_1\times \sin r=n_2\times \frac{n_1}{n_2}$
$⟹\sin r=1$
$⟹r={90}^o$