# A student is investigating the photoelectric effect using two different metals. Metal A releases electrons when exposed to violet light but not when exposed to green light. Metal B releases electrons when exposed to ultraviolet light but not when exposed to violet light. Explain why electrons are released from Metal A by violet light but not by green light, and why Metal B requires ultraviolet light to release electrons.

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

> In the photoelectric effect, light shining on a metal surface can cause electrons to be emitted. Whether electrons are emitted depends on the frequency of the light used and the metal being investigated.

## Mark scheme (5 marks)

1. Light exists as discrete packets of energy called photons
2. The energy of a photon depends on its frequency — higher frequency means higher energy photon
3. Each electron can only absorb one photon, so the energy of a single photon must be sufficient to release an electron
4. Green light photons do not have enough energy to release electrons from Metal A / violet photons have sufficient energy to overcome the energy needed to free an electron from Metal A
5. Metal B requires a higher minimum energy to release electrons than Metal A, so only the higher frequency ultraviolet photons have sufficient energy

## Key terms

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

## 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/a-student-is-investigating-the-photoelectric-33b77af3) · Published by Druglandscape Ltd.