A student plucks a guitar string and produces a sound wave. The sound wave is described as a longitudinal wave. Explain what is meant by a longitudinal wave and describe two other features of waves that apply to both longitudinal and transverse waves.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
When a guitar string is plucked, it vibrates and produces a sound wave that travels through the air to a listener's ears.
Model answer (4 marks)
A longitudinal wave is one in which the particles of the medium vibrate parallel to the direction the wave travels.
Two features common to all waves are:
1. Energy transfer – waves carry energy from one place to another without moving the medium itself.
2. Amplitude – the maximum displacement of a particle from its equilibrium position.
Two features common to all waves are:
1. Energy transfer – waves carry energy from one place to another without moving the medium itself.
2. Amplitude – the maximum displacement of a particle from its equilibrium position.
Examiner tips
- Use the exact definition of a longitudinal wave – parallel vibrations. Mention energy transfer and amplitude as the two common features. Keep the answer concise and avoid extra wording.
Common mistakes
- Confusing longitudinal with transverse; describing particle motion perpendicular to wave travel. Forgetting that the medium does not move with the wave. Including wavelength or frequency as the common feature instead of amplitude.
Mark scheme (4 marks)
- In a longitudinal wave the vibrations (oscillations) are parallel to the direction of wave travel / energy transfer
- Waves transfer energy from one place to another without transferring matter / the medium does not travel with the wave
- Amplitude is the maximum displacement of a point on the wave from its rest / equilibrium position
- Wavelength is the distance between two successive points that are in phase (e.g. crest to crest or compression to compression) OR frequency is the number of complete waves passing a point per second
Key terms in this question
Related
- All Eduqas GCSE Physics revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
More Features of waves questions
- A sound wave travelling through air has a frequency of 440 Hz and a wavelength o…
- Waves transfer energy from one place to another. Describe the key features of a …
- A ripple on the surface of water is an example of a transverse wave. Describe th…
- A police siren produces a sound wave. Explain what is meant by the amplitude and…