Parts of the eye

What this diagram shows

The eye works a little like a camera. Light enters through the clear cornea, passes through the pupil (the hole in the colored iris), is focused by the lens and lands on the retina at the back. The retina turns light into nerve signals, and the optic nerve carries them to the brain. This side-view diagram draws light rays coming in from the left so the path is easy to follow. Explore, Labels and Quiz me work as on our other diagrams.

The light slider shows the pupil reflex. In dim light the pupil opens wide, up to about 8 mm, to let in more light. In bright light the iris makes it as small as about 2 mm. The front view below the slider shows the same change the way you would see it in a mirror.

Why seeing the pupil change helps

The pupil reflex is something students can test on themselves, which makes it memorable. After using the slider, ask them to look in a mirror in a dim room, then switch on the light. The pupils shrink within a second or so. Connecting the model to their own body turns a label into an idea.

Common misconceptions

• The pupil is not a black dot on the eye. It is a hole, and it looks black because light goes in and very little comes back out.
• We do not see because light comes out of our eyes. Light from a source, or reflected off objects, travels into the eye.
• The lens is not the only part that focuses. The cornea does most of the bending of light, and the lens fine-tunes the focus.
• The image on the retina is upside down. The brain makes sense of it, so the world looks the right way up.

A 10-minute eye activity

• Ask the student to draw how they think light gets from a lamp to their eye.
• Tap each part in Explore in the order light reaches it: cornea, pupil, lens, retina, then the optic nerve.
• Move the slider from dark to bright and back, then try the Predict the pupil challenge.
• Use a mirror to watch a real pupil change. Never look at the sun or straight into a bright lamp.
• Compare a new drawing with the first one.

Where this fits in school

• US, grade 4: NGSS 4-PS4-2 asks students to model how light reflecting from objects enters the eye so objects can be seen, and 4-LS1-2 looks at how senses send information to the brain.
• US, grades 6 to 8: NGSS MS-LS1-8 asks how sensory receptors respond to stimuli by sending messages to the brain.
• England, Year 6: pupils explain that objects are seen because they give out or reflect light into the eye.
• England, Key Stage 3 and GCSE: students meet the retina as a light-sensitive surface, and GCSE Biology looks at the eye's structure and the pupil reflex in more detail.

Learning more

Science is part of Eurekami's skill map, with lessons that draw science diagrams live and narrate them in English or Spanish. When a question is tricky, the AI tutor asks guiding questions so the student does the reasoning. For older students, Exam Prep includes GCSE Combined Science practice papers.