Question

A light ray is incident normally on a plane mirror.

(a) What is the angle of incidence?

(b) What is the path of reflected ray?

• A. $\left(a\right){180}^{\circ },\left(b\right)$ same as incident ray
• B. $\left(a\right){180}^{\circ },\left(b\right)$ opposite to incident ray
• C. $\left(a\right)0^{\circ },\left(b\right)$ opposite to incident ray
• D. $\left(a\right)0^{\circ },\left(b\right)$ same as incident ray

Answer 1

Answer: (C)

Case (a):
If a ray of light is incident normal to the surface of the plane mirror, then the angle of incidence is $0^0$, as the normal passes perpendicularly to the mirror.
Case (b):
The Second Law of Reflection states that the angle of incidence is always equal to the angle of reflection. Therefore, the angle of reflection is same as the angle of incidence, that is, $0^0$. So, the reflected ray will retrace the path of the incident ray.