Let the light in!

Let the light in!

How do your pupils work?

Your eyes detect light. Light gets into your eye through your pupil.

The light travels through your pupil to the retina, light-sensitive cells at the back of your eye.

Your retina changes the light into a nerve signal. The nerve signal travels along the optic nerve to your brain. Your brain decodes the light and decides what to do with the visual information.

Your pupil is very clever. Your retina can be damaged by too much light. In bright light, your pupil becomes smaller to keep out some of the light.

In dim light, it can be hard to see. Your pupil becomes bigger to let more light in.


Your pupils get bigger to let more light in and get smaller to protect your retina

Try this!

Ask a friend or parent to volunteer. Dim the lights in a room or close the curtains a bit. After a few minutes, look into the eyes of your volunteer and check the size of their pupils.

Turn the lights back on and open the curtains. Look at the size of your volunteer's pupils again. Have they got smaller?

When you turn the lights on again, muscles in your volunteer's eye move to make the pupil smaller. This stops too much light getting in, which would damage the retina.

Curriculum information