# A person walks from a brightly lit street into a dark cinema. Explain how the eye responds to this change in light intensity, and describe how the structure of the retina allows the person to see in the dim light inside the cinema.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 4.4 Vision and hearing · Explain · 5 marks

> The human eye contains two types of photoreceptor cells in the retina — rod cells and cone cells. These cells detect light and send nerve impulses to the brain via the optic nerve.

## Mark scheme (5 marks)

1. The pupil dilates (gets wider/larger) in dim light
2. The iris controls the size of the pupil / circular muscles relax and radial muscles contract
3. This allows more light to enter the eye
4. Rod cells are sensitive to low light intensities / rod cells are used in dim light
5. Rod cells cannot distinguish colour / rod cells are not sensitive to colour, only to light and dark

## Key terms

- [retina](https://www.gradenine.co.uk/glossary/retina)

## Related

- [Revision notes for Edexcel A-Level Biology A: Salters-Nuffield (9BN0)](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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Source: [GradeNine](https://www.gradenine.co.uk/q/a-person-walks-from-a-brightly-f83e1699) · Published by Druglandscape Ltd.