For a ray incident normally on a plane mirror, the angle of incidence is :
(a) 90°
(b) 45°
(c) 30°
(d) 0°

(d) 0°

Reason — For a ray incident normally on a plane mirror, the angle of incidence is i = 0°, therefore the angle of reflection r = 0°. Thus, a ray of light incident normally on a mirror is reflected along the same path.