# Explain how the structure of the eye allows a person to see an object clearly when light enters the eye.

> Pearson Edexcel A-Level Biology A (9BI0) — 4.4 Vision and hearing · Explain · 5 marks

> The human eye contains several structures that work together to focus light onto the retina. When light from an object enters the eye, it must be refracted so that a sharp image is formed.

## Mark scheme (5 marks)

1. Light enters the eye through the cornea, which refracts (bends) the light
2. The lens also refracts the light / fine-tunes the focusing of light
3. The iris controls the size of the pupil, regulating the amount of light entering the eye
4. Light is focused onto the retina at the back of the eye
5. The retina contains receptor cells (rods and cones) that detect light and send electrical impulses along the optic nerve to the brain

## Related

- [Revision notes for Pearson Edexcel A-Level Biology A (9BI0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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