Question

For light incident from air onto a slab of refractive index $2$ , maximum possible angle of refraction is

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

Answer 1

Answer: (D)

The situation is shown in figure

Applying the Snells law at air-glass interface, we get
${\mu }_{1}sini={\mu }_{2}sinr$
or $sinr=\frac{{\mu }_1}{{\mu }_2}sini=\frac{1}{2}sini$
For the maximum angle of refraction, $i=90^{\circ }$
$\therefore sinr=\frac{1}{2}sin90^{\circ }=\frac{1}{2}$
or $r=si{n}^{-1}\left(\frac{1}{2}\right)=30^{\circ }$