Question

A ray of light is incident normally on a plane mirror what will be the angle of incidence?

Answer 1

Explanation:

For a plane mirror: If the incident ray falls along the normal, the angle of incidence is 0 degrees, NOT 90 degrees. The angle is measured with the normal to the mirror and not with the plane of the mirror. Hence the angle of reflection is equal to 0 degrees.

ANSWER

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.