Question

A ray of light is incident normally on one of the faces of a prism of apex angle $30^\circ $ and refractive index $\sqrt{2}$ . The angle of deviation of the ray is

• A. $30 ^\circ $
• B. $45 ^\circ $
• C. $15 ^\circ $
• D. none of these

Answer 1

Answer: (C)

Using Snell’s law for the refraction at $AC$ , we get
$\mu \, sini=\left(\right.1\left.\right) \, sinr$
$\sqrt{2}sin30^\circ =sinr$
$sinr=\frac{1}{\sqrt{2}}$
$\Rightarrow \, r=45^\circ $
$\therefore $ Angle of deviation $=45^\circ -30^\circ =15^\circ $