# Earthquakes produce two types of seismic wave: P-waves and S-waves. Explain the differences between P-waves and S-waves, including how the behaviour of these waves as they travel through the Earth's interior can be used to determine that the Earth has a liquid outer core.

> WJEC A-Level Physics (Wales) — 5.3 Electric and magnetic fields (A-Level only) · Explain · 5 marks

## Mark scheme (5 marks)

1. P-waves are longitudinal waves (oscillations parallel to direction of travel/energy transfer)
2. S-waves are transverse waves (oscillations perpendicular to direction of travel/energy transfer)
3. P-waves travel faster than S-waves / S-waves travel slower than P-waves
4. S-waves cannot travel through fluids / liquids (whereas P-waves can travel through all mediums)
5. S-waves are not detected on the opposite side of the Earth (in the shadow zone), showing the outer core must be liquid

## Key terms

- [P-waves](https://www.gradenine.co.uk/glossary/p-waves)
- [S-waves](https://www.gradenine.co.uk/glossary/s-waves)

## 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/earthquakes-produce-two-types-of-seismic-cdd6625d) · Published by Druglandscape Ltd.