Question

A Ray of light is incident on a plane mirror making an angle of ${90^ \circ }$ with the mirror surface. What will be the angle of reflection for the ray of light?
A. ${45^ \circ }$
B. ${90^ \circ }$
C. ${0^ \circ }$
D. ${60^ \circ }$

Answer 1

Hint:We can use the laws of reflection to solve this question. According to the law of reflection angle of incidence and angle of reflection should be equal. Angle of incidence is the angle between the incident ray and the normal to the surface at the point of incidence.

Complete step-by-step solution:
In this question it is given that a ray of light is falling on a plane mirror.
It makes an angle of ${90^ \circ }$ with the surface of the mirror.
We are asked to find the angle of reflection for the Ray of light.
In order to solve this problem, we need to know the laws of reflection.
There are two laws of reflection. They are
(1) the incident ray reflected ray and the normal lies in the same plane.
(2) the angle of incidence will be equal to the angle of reflection.
Here, the incident ray is the ray that is falling. The normal is the line drawn at the point of incidence perpendicular to the surface of the mirror.
We know that the angle between the incident ray and the normal is the angle of incidence.
The angle between the reflected ray and the normal is known as the angle of reflection.
It is already given that the incident ray is making an angle of ${90^ \circ }$ with the mirror surface. This means the incident ray coincides with the normal line drawn at the point of incidence. So there will not be any angle between the incident ray and normal. Thus, the angle of incidence is zero.
We know according to the law of reflection angle of incidence and angle of reflection should be equal. Since angle of incidence is zero the angle of refraction should also be zero.
Thus, the correct answer is option C.

Note:- Always remember that the angle of incidence is the angle between the incident ray and the perpendicular line drawn at the point of incidence. Don’t think that the given angle ${90^ \circ }$ is the angle of incidence. it is only the angle between the mirror surface and the incident ray. Angle of reflection is equal to the angle of incidence which is the angle between incident ray and normal.