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Mirrors

Waves, sound and light · level 2, lesson 4 of 6

A question to start

Some ambulances have the word "AMBULANCE" painted backwards on the front. Why would anyone write a word backwards?

The idea

A mirror is very smooth and shiny, so it reflects light neatly. Light that hits a mirror bounces off at the same angle it came in, like a ball bouncing off a wall.

When you look in a mirror, you see an image of yourself. The image is the right way up, but it is reversed left to right: raise your right hand and the person in the mirror raises their left.

light inlight outmirror: equal angles

Worked examples

1. The ambulance. A driver ahead sees the ambulance in their mirror. The mirror reverses the backwards word, so it reads "AMBULANCE" the right way round.

2. A periscope uses two mirrors to bounce light over a wall, so you can see over it while staying hidden.

3. Spotting a friend. If you can see your friend's eyes in a mirror, they can see yours. Light takes the same path both ways.

Try it

  1. Why is a mirror so good at reflecting light?
  2. You wave your left hand at a mirror. Which hand does your image wave?
  3. How many mirrors does a simple periscope use?
  4. Write your name so that it reads the right way round in a mirror.
Answers
  1. It is very smooth and shiny.
  2. Its right hand (the one on the same side as your left).
  3. Two.
  4. Write each letter back to front, from right to left, then check it in a mirror.

Common mistake

"Mirrors turn things upside down." A flat mirror keeps things the right way up. It only swaps left and right.

Where it leads