# A solar cell is illuminated with ultraviolet light of a certain frequency. Electrons are released from the surface of the solar cell material. When the ultraviolet source is replaced with a dim green light source, no electrons are released. Explain these observations in terms of photons and the photoelectric effect.

> WJEC A-Level Physics (Wales) — 2.7 Photons · Explain · 5 marks

## Mark scheme (5 marks)

1. Light travels as discrete packets of energy called photons
2. The energy of a photon depends on its frequency (higher frequency = higher energy photon)
3. A single photon must supply enough energy to release one electron (equal to or greater than the work function)
4. Ultraviolet light has a higher frequency than green light, so each UV photon has more energy, which is sufficient to release electrons
5. Green light photons have insufficient energy (below the threshold frequency/work function) so no electrons are released regardless of intensity

## Key terms

- [photon](https://www.gradenine.co.uk/glossary/photon)
- [photoelectric effect](https://www.gradenine.co.uk/glossary/photoelectric-effect)
- [frequency](https://www.gradenine.co.uk/glossary/frequency)

## Related

- [Revision notes for WJEC A-Level Physics (Wales)](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-solar-cell-is-illuminated-with-ccb2b87b) · Published by Druglandscape Ltd.