# Explain why increasing the frequency of light shone onto a metal surface causes electrons to be emitted with greater kinetic energy, even when the intensity of the light is kept the same.

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

> Light can cause electrons to be released from the surface of a metal. This is known as the photoelectric effect. Scientists found that the kinetic energy of the emitted electrons depends on the frequency of the light used, not its intensity.

## Mark scheme (5 marks)

1. Light is made up of photons (discrete packets/quanta of energy)
2. The energy of a photon depends on (is proportional to) its frequency
3. A single photon interacts with a single electron (one-to-one interaction)
4. Some photon energy is used to free the electron from the surface (work function / threshold energy)
5. The remaining/extra energy becomes the kinetic energy of the electron, so higher frequency photons give electrons greater kinetic energy

## Key terms

- [frequency](https://www.gradenine.co.uk/glossary/frequency)
- [kinetic energy](https://www.gradenine.co.uk/glossary/kinetic-energy)

## 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/explain-why-increasing-the-frequency-of-bec1c544) · Published by Druglandscape Ltd.