Light and reflection

Light travels in straight lines, far faster than sound. We see objects when light from them enters our eyes. Mirrors reflect light so that the angle of incidence equals the angle of reflection.

Key facts

  • Light travels in straight lines; shadows form where it’s blocked.
  • Luminous objects give out light; we see everything else by reflected light.
  • Law of reflection: angle of incidence = angle of reflection (measured from the normal).
  • Smooth surfaces give clear reflections (specular); rough ones scatter light (diffuse).

Worked examples

Example 1

A ray hits a mirror at 35° to the mirror surface. What is the angle of reflection?

  1. The normal is at 90° to the mirror.
  2. Angle of incidence: 90 − 35 = 55°.
  3. Angle of reflection = 55°.

Answer: 55°