# A student is investigating the emission of electrons from a metal surface. They find that green light does not cause any electrons to be emitted from the surface, no matter how long the light is shone onto it. However, when violet light is used instead, electrons are emitted immediately. Explain why green light fails to release electrons from this metal surface, and why violet light is able to do so.

> WJEC A-Level Physics (Wales) — 3.2 Photon and particle properties · Explain · 5 marks

## Mark scheme (5 marks)

1. Light travels as photons (packets/quanta of energy)
2. The energy of a photon depends on the frequency of the light
3. Violet light has a higher frequency than green light, so violet photons carry more energy
4. Each photon interacts with one electron — if a single photon does not have enough energy to overcome the work function, no electron is released
5. Violet photon energy meets or exceeds the work function, so electrons are released immediately

## 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-student-is-investigating-the-emission-5a8c0a19) · Published by Druglandscape Ltd.