Question

A ray of light travelling in water is incident on its surface open to air, The angle of incidence is $\theta $, which is less than the critical angle, then there will be,
(A) Only a reflected 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^\circ - 2\theta $
(D) A reflected ray and a refracted ray and the angle between them would be greater than $180^\circ - 2\theta $

Answer 1

Hint It seems like a confusing question, but this is an easy question if you know the concept of total internal reflection. Try to draw a diagram using given information for better understanding. From the diagram you have drawn you can easily answer the question.

Complete step by step answer
Angle of incidence is defined as the angle between a ray incident on a surface and the line perpendicular to the surface at the point of incidence.
When a ray of light hits a smooth polished surface, the light ray bounces back, it is called the reflection. The angle at which it bounce back is known as the angle of reflection
When light waves move from one medium to another, there is a change in the direction of waves due to the obstacles, so they bend and continue to pass it is known as refraction. The angle at which it bends is known as angle of refraction.
The critical angle is the angle of incidence beyond which light rays passing through a denser medium to the surface of a less dense medium are no longer refracted but totally reflected.
The condition for total internal reflection is
The light must travel from a denser medium to a rarer medium
The angle of incidence in the denser medium must be greater than the critical angle.
Given,


A ray of light travelling in water is incident on its surface open to air whi8ch means the light is travelling from the denser medium to rarer medium
If a light travels from denser to rarer medium hen the light gets partially reflected and partially refracted as shown in the diagram
It is also given that angle of incidence, $\theta $ is less than the critical angle.
Then the angle between the refracted angle and reflected angle will be less than $180^\circ - 2\theta $ as given in the diagram.

From the above discussion, the correct answer is option (C) A reflected ray and a refracted ray and the angle between them would be less than $180^\circ - 2\theta $

Note Here even though the light travels from a denser medium to a rarer, medium the angle of incidence is less than the critical angle. So, the total internal reflection will not take place in this case.