Question

A light ray is incident normally on a plane mirror. What is the direction of reflected ray? Show it on a diagram.

Answer 1

From the law of reflection, angle of incidence is equal to the angle of reflection, i.e., $\angle i=\angle r$.
In this case, $\angle i=0$. Following laws of reflection, $\angle r=0^{\circ }$, which implies reflected ray will retrace the path of incident ray.