Question

A ray of light travelling in water is incident on its surface open to air. The angle of incidence $\theta ,$ which is less than the critical angle. Then there will be:

• A. only a reflected ray and no refracted ray
• B. only a refracted ray and no reflected ray
• C. a reflected ray and a refracted ray and the angle between them would be less than ${180}^o-2\theta$
• D. a reflected ray and a refracted ray and the angle between them would be greater than ${180}^o-2\theta$

Answer 1

Answer: (C)

a reflected ray and a refracted ray and the angle between them would be less than ${180}^o-2\theta$

As $\theta$ is less than critical angle, some portion of the light is reflected and some are refracted.

Clearly from the diagram, $2\theta +8+\alpha =180°$

$\Rightarrow 8=(180°-2\theta )-\alpha$

$8<(180°-2\theta ).$

Hence, the answer is a reflected ray and a refracted ray and the angle between them would be less than $180°-2\theta .$