Lesson: Chapter 5 — Optics

5.1. Reflection at a plane mirror 2 of 4

The laws of reflection

Every reflection obeys two laws, which you have met in earlier grades.

First law

The incident ray, the reflected ray and the normal at the point of incidence all lie in the same plane.

Second law

The angle of incidence equals the angle of reflection.

The second law

i = r

A ray striking the pole of a curved mirror at an angle to the axis, reflected at an equal angle on the other side of the axis — the law holds at every mirror.

At the pole the axis is the normal, so the ray leaves at the same angle to the axis as it arrived.