Physics

Physics

Problem

A light ray makes an angle of 0.40 rad0.40\,\text{rad} with the surface of a plane mirror. The angle of reflection, expressed in radians, is closest to a) 0.800.80 b) 1.171.17 c) 1.261.26 d) 0.400.40
Intuitive explanation

The key is recognizing that the angle of incidence (and angle of reflection) is measured from the normal to the surface, not from the surface itself. Since your ray makes 0.40 rad0.40\,\text{rad} with the surface, you need to find the complementary angle to get the angle from the normal. By the law of reflection, the angle of reflection equals the angle of incidence—both measured from that normal line.

Intuitive explanation

The key is recognizing that the angle of incidence (and angle of reflection) is measured from the normal to the surface, not from the surface itself. Since your ray makes 0.40 rad0.40\,\text{rad} with the surface, you need to find the complementary angle to get the angle from the normal. By the law of reflection, the angle of reflection equals the angle of incidence—both measured from that normal line.

Browse the problem library