Question

A ray of light is incident at an angle of ${60}^o$ on one face of a prism of angle ${30}^o$. The ray emerging out of the prism makes an angle of ${30}^o$ the incident ray is

• A. Normal to the face through which it emerges
• B. Inclined at ${30}^o$ to the face through which is emerges
• C. Inclined at ${60}^o$ to the face through which it emerges
• D. None of these

Answer 1

Answer: (A)

Normal to the face through which it emerges

We know that $\delta =i+e-A\Rightarrow e=\delta +A-i$
$={30}^o+{30}^o-{60}^o=0^o$
$\therefore$ Emergent ray will be perpendicular to the face.Therefore it will make an angle of ${90}^o$ with the face through which it emerges.