# A scientist investigates the photoelectric effect using a clean caesium metal surface. When light of a certain frequency is shone on the surface, electrons are emitted. The scientist then doubles the intensity of the light while keeping the frequency the same. Describe and explain what happens to the number of electrons emitted per second and the maximum kinetic energy of the emitted electrons when the intensity is doubled.

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

## Mark scheme (5 marks)

1. The number of electrons emitted per second increases when intensity is doubled
2. Higher intensity means more photons arriving per second
3. Each photon interacts with one electron, so more photons cause more electrons to be emitted
4. The maximum kinetic energy of the emitted electrons does not change
5. Maximum kinetic energy depends only on the frequency (or energy) of each photon, not on intensity

## Key terms

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

## Related

- [Revision notes for Eduqas A-Level Physics](https://www.gradenine.co.uk/learn)
- [How to answer "Describe and 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-scientist-investigates-the-photoelectric-effect-833c1718) · Published by Druglandscape Ltd.