Question

when does a ray of light falling on a plane mirror completely retrace its path?​

Answer 1

Explanation:

According to law of reflection of light, the incident ray is always equal to the reflected ray . So, if the ray falls normally on a plane mirror then the incident ray as well as the reflected ray becomes 0o . Therefore , it retraces it path.

Answer 2

The plane mirror completely retraces its path is at the centre of curvature !!:)