# A person enters a dark cinema after being outside in bright sunlight. At first they cannot see clearly, but after a few minutes their vision improves. Explain how the eye responds to the change in light intensity when the person first enters the dark cinema, and why their vision improves over time.

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

## Mark scheme (5 marks)

1. The pupil is the structure that controls how much light enters the eye
2. In low/dim light the circular muscles of the iris relax and the radial muscles contract
3. This causes the pupil to dilate/widen/become larger, allowing more light to enter
4. The retina contains receptor cells (rods and cones) that detect light
5. Over time the rod cells become more sensitive to the low light levels, so more nerve impulses are sent to the brain via the optic nerve, improving vision

## 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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Source: [GradeNine](https://www.gradenine.co.uk/q/a-person-enters-a-dark-cinema-1fb2a77e) · Published by Druglandscape Ltd.