# A student investigates the effect of light intensity on the rate of photosynthesis in pondweed. She places the pondweed at different distances from a lamp and counts the number of bubbles produced per minute. Explain why the rate of photosynthesis decreases as the pondweed is moved further away from the lamp.

> Edexcel GCSE Biology (1BI0) — 6.1 Photosynthesis · Explain · 4 marks

> A student investigates the effect of light intensity on the rate of photosynthesis in pondweed. She places the pondweed at different distances from a lamp and counts the number of bubbles produced per minute.

## Mark scheme (4 marks)

1. As distance increases, light intensity decreases
2. Light is a limiting factor for photosynthesis
3. Less light energy is available for photosynthesis / to convert light energy into chemical energy
4. So less glucose (and oxygen) is produced per minute / rate of photosynthesis decreases

## Key terms

- [photosynthesis](https://www.gradenine.co.uk/glossary/photosynthesis)
- [light intensity](https://www.gradenine.co.uk/glossary/light-intensity)

## Related

- [Revision notes for Edexcel GCSE Biology (1BI0)](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-student-investigates-the-effect-of-76538d89) · Published by Druglandscape Ltd.