Question

A horizontal ray of light passes through a prism of refractive index 1.5 and apex angle 4${}^o$ and then strikes a vertical plane mirror placed mirror placed to the right to the prism. If after reflection, the ray is to be horizontal, then the mirror must be rotated through an angle:

• A. 1${}^{\circ }$
• B. 2${}^{\circ }$
• C. 3${}^{\circ }$
• D. 4${}^{\circ }$

Answer 1

The correct option is A 1${}^{\circ }$

Given,

$A=4^{\circ }$

$\mu =1.5$
$\delta =(\mu -1)A=4\times \frac{1}{2}=2^{\circ }$
The mirror should be rotated by $\delta /2=1^{\circ }$