Earthquakes produce two types of seismic wave: P-waves and S-waves. Describe the differences between P-waves and S-waves in terms of their nature, speed, and ability to travel through different materials.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Scientists use seismic waves produced by earthquakes to study the internal structure of the Earth. By monitoring which waves are detected at different points on the Earth's surface, scientists can draw conclusions about the materials that make up the Earth's interior.
Model answer (5 marks)
P‑waves are longitudinal waves, with particle motion parallel to the direction of travel.
S‑waves are transverse waves, with particle motion perpendicular to the direction of travel.
P‑waves travel faster than S‑waves.
P‑waves can propagate through all media – solids, liquids and gases.
S‑waves cannot propagate through fluids – they are blocked by liquids and gases.
S‑waves are transverse waves, with particle motion perpendicular to the direction of travel.
P‑waves travel faster than S‑waves.
P‑waves can propagate through all media – solids, liquids and gases.
S‑waves cannot propagate through fluids – they are blocked by liquids and gases.
Examiner tips
- Use the word ‘longitudinal’ for P‑waves and ‘transverse’ for S‑waves. State the speed order explicitly. Mention the media each wave can or cannot travel through. Keep each point short and to the point.
Common mistakes
- Confusing longitudinal with transverse. Forgetting that S‑waves cannot travel through liquids. Using vague terms like ‘fast’ without comparison. Including unnecessary detail such as wave frequency.
Mark scheme (5 marks)
- P-waves are longitudinal waves (oscillations parallel to direction of travel/energy transfer)
- S-waves are transverse waves (oscillations perpendicular to direction of travel/energy transfer)
- P-waves travel faster than S-waves
- P-waves can travel through all mediums (solids, liquids and gases)
- S-waves cannot travel through fluids (liquids or gases)
Key terms in this question
Related
- All Eduqas A-Level Physics revision notes →
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- Decode the mark scheme abbreviations →
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