Answer: Angle of reflection of light or a wave is the angle between the normal line of the reflective surface and the reflected ray.
Explanation:A reflective surface for a light ray causes the ray bouncing back. If a light ray incidence to a smooth surface perpendicularly it bounces back perpendicularly. But if the ray incidences at an angle with the normal of the surface it reflects from the surface by making the same angle.
Q(incidence) = Q(reflection) for a smooth surface of plane mirror.