Longitudinal Waves (Edexcel International A Level Physics)

Revision Note

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Lindsay Gilmour



Longitudinal Waves

Longitudinal Waves

  • A longitudinal wave is one where the particles oscillate parallel to the;
    • Propagation of the wave
    • Direction of energy transfer
  • Longitudinal waves show areas of
    • High pressure, called compressions
    • Low pressure, called rarefactions

Longitudinal wave diagram, downloadable AS & A Level Physics revision notes

Diagram of a longitudinal wave


  • Examples of longitudinal waves are:
    • Sound waves
    • Ultrasound waves
    • P-waves caused by earthquakes

  • Longitudinal waves cannot be polarised

Labelling Longitudinal Waves

  • You learned how to describe the properties of a wave, such as amplitude and wavelength at the start of this topic
    • The diagram shows a wavelength on a longitudinal wave

Wavelength on transverse and longitudinal waves, downloadable AS & A Level Physics revision notes

Wavelength is shown on a longitudinal wave


Exam Tip

Questions about longitudinal waves typically start by asking for a definition, so be ready with a statement about areas of high and low pressure and the keywords compression and rarefaction.

Be careful with graphs of waves and don't assume a sinusoidal-shaped graph represents a transverse wave. Longitudinal waves can also look sinusoidal when plotted on a graph - make sure you read the question and look for whether the wave travels parallel (longitudinal) or perpendicular (transverse) to the direction of travel to confirm which type of wave it is.

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Lindsay Gilmour

Author: Lindsay Gilmour

Lindsay graduated with First Class Honours from the University of Greenwich and earned her Science Communication MSc at Imperial College London. Now with many years’ experience as a Head of Physics and Examiner for A Level and IGCSE Physics (and Biology!), her love of communicating, educating and Physics has brought her to Save My Exams where she hopes to help as many students as possible on their next steps.

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