Question

In Fig, $PQ$ and $PR$ are the two light rays emerging from an object $P$. The ray $PQ$ is refracted as $QS$. State the special name given to the angle of incidence $\angle PQN$ of the ray $PQ$ :

• A. Critical angle
• B. Normal angle
• C. Refracted angle
• D. Reflected angle

Answer 1

The correct option is A Critical angle

Critical angle is the angle of incidence for which the angle of refraction is ${90}^o$. The ray QS has an angle of refraction ${90}^o$. Hence, $\angle PQN$ is the critical angle.