A musician plucks a guitar string. The string vibrates and produces a sound wave that travels through the air to a listener. Explain how the amplitude and frequency of the sound wave affect what the listener hears.

WJEC GCSE Physics (Wales) — 1.5 Features of waves · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Amplitude determines the loudness of the sound: a larger amplitude means the air particles are displaced more, so the wave carries more energy and the sound is louder.
Frequency determines the pitch of the sound: a higher frequency means more wave crests pass a point each second (shorter period), so the listener hears a higher‑pitched tone.

Examiner tips

  • Use the terms "loudness" and "pitch" explicitly. Show the relationship between amplitude and energy, and between frequency and period. Keep each point short and to the point to match the 4‑mark structure.

Common mistakes

  • Confusing amplitude with frequency, or vice versa. Using vague words like "stronger" or "higher" without linking to loudness or pitch. Omitting the link between frequency and period or energy carried by the wave.

Mark scheme (4 marks)

  1. Amplitude is related to the loudness of the sound
  2. A greater amplitude means more energy is carried by the wave
  3. Frequency is related to the pitch of the sound
  4. A higher frequency means more waves arrive per second / the waves have a shorter period

Key terms in this question

amplitude · frequency

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