# Reflection

A wave bounces off a surface. The angle of incidence equals the angle of reflection, both measured from the normal (a line at right angles to the surface).

Physics (school) · Part 05: Waves, sound and light · Card 4 of 8 · Last updated 2026-10-19

## Analogy

A ball bouncing off a wall at the same angle it arrived.

## Example

**Mirror**

Light hits a mirror at 30 degrees
to the normal.
It leaves at 30 degrees
to the normal on the other side.

## In practice

A mirror works by reflection. An echo is a reflected sound.

## Practice

### Flashcards

- **State the law of reflection.** The angle of incidence equals the angle of reflection.

## Questions people ask

### What is the normal in a ray diagram?

The normal is an imaginary line drawn at 90 degrees to the surface at the point where the ray hits. Angles of incidence and reflection are measured from this line, not from the surface itself. Drawing it with a dashed line helps keep the angles correct.

### Why can I see myself in a mirror but not on a wall?

A mirror is smooth, so parallel rays all bounce off at the same angle and form a clear image. A wall is rough, so rays scatter in many directions, which is called diffuse reflection. You can still see the wall, but it gives no clear picture.

## Related concepts

- [Refraction](https://studyvisually.com/learn/science/physics-school/physics-school-part-5/physics-school-part-5-concept-5)
- [Electromagnetic spectrum](https://studyvisually.com/learn/science/physics-school/physics-school-part-5/physics-school-part-5-concept-6)
- [Waves](https://studyvisually.com/learn/science/physics-school/physics-school-part-5/physics-school-part-5-concept-1)
- [Amplitude, wavelength and frequency](https://studyvisually.com/learn/science/physics-school/physics-school-part-5/physics-school-part-5-concept-2)

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