# Explain what a photon is and why higher frequency light transfers more energy to a metal surface than lower frequency light of the same intensity.

> Eduqas A-Level Physics — 2.7 Photons · Explain · 5 marks

> Scientists studying the photoelectric effect found that ultraviolet light could eject electrons from a metal surface, but red light of the same intensity could not, no matter how long it shone on the surface.

## Mark scheme (5 marks)

1. A photon is a packet (quantum) of electromagnetic energy
2. The energy of a photon depends on its frequency / higher frequency means higher energy photon
3. Each photon interacts with one electron (one-to-one interaction)
4. If the photon energy is below the threshold / minimum energy needed to free an electron, no electrons are ejected regardless of intensity
5. Higher frequency photons have enough energy to eject electrons because each individual photon carries sufficient energy to overcome the energy holding the electron in the metal

## Key terms

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

## 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)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-what-a-photon-is-and-2aebd9c0) · Published by Druglandscape Ltd.