# Explain why increasing the frequency of light incident on a metal surface causes electrons to be emitted with greater kinetic energy, whereas increasing the intensity of light of the same frequency does not increase the kinetic energy of the emitted electrons.

> Eduqas A-Level Physics — 3.2 Photon and particle properties · Explain · 5 marks

> When light shines on a metal surface, electrons can be emitted. This is known as the photoelectric effect. Scientists found that the kinetic energy of 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 its frequency (E = hf, or energy is proportional to frequency)
3. A single photon interacts with a single electron, transferring all its energy to that electron
4. Any energy above the work function (the minimum energy needed to release the electron from the surface) becomes kinetic energy of the emitted electron
5. Increasing intensity increases the number of photons but not the energy of each photon, so each electron still receives the same energy and is emitted with the same kinetic energy

## Key terms

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

## Related

- [Revision notes for Eduqas A-Level Physics](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)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-increasing-the-frequency-of-a6f1c33b) · Published by Druglandscape Ltd.