Question

A ray of light passes through an equilateral prism (refractive index 1.5) such that angle of incidence is equal to angle of emergence and the latter is equal to ${3/4}^{th}$ of the angle of prism. The angle of deviation is

• A. ${60}^{\circ }$
• B. ${30}^{\circ }$
• C. ${45}^{\circ }$
• D. ${120}^{\circ }$

Answer 1

The correct option is B ${30}^{\circ }$

$\delta =i+e-A$

given $i=e=\frac{3}{4}A$

$\delta =\frac{3}{4}A+\frac{3}{4}A-A$

$\angle A={60}^o$ ( equilateral prism)

$\delta =\frac{A}{2}=\frac{60}{2}={30}^o$

$\therefore \delta =30$