Parts of a Longitudinal Wave

A sound wave in air, from its vibrating source to its compressions and rarefactions.

Parts of a Longitudinal Wave

Name Date

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1 2 3 4 5 6
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Write the name of each numbered part.Answer key

  1. Source (vibrating object)
  2. Compression
  3. Rarefaction
  4. Wavelength
  5. Medium (particles)
  6. Particle motion

Drawn for this site by script, 2026-09-26. Licence: own work.

Each numbered ring is a button. Use the arrow keys to move between them and Enter to choose. Names are read out in Study, and once a part is answered.

Next step Next: the other kind, a transverse wave

All 6 parts on the diagram

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Start here: 4 main parts 4

  1. Source (vibrating object) The vibrating object that makes the wave. Examples are a speaker cone or a guitar string.
  2. Compression A region where the particles are pushed close together, at higher pressure.
  3. Rarefaction A region where the particles are spread apart, at lower pressure.
  4. Wavelength The length of one whole wave, from one compression to the next.

Other 2

  1. Medium (particles) The material the wave travels through, here the particles of air.
  2. Particle motion Back and forth along the direction the wave travels. In a longitudinal wave each particle moves this way, then returns.

How this list was compiled: Read 2026-09-26. (1) OpenStax Physics, 13.1 Types of Waves, https://openstax.org/books/physics/pages/13-1-types-of-waves : in a longitudinal wave the medium moves parallel to the direction of propagation; compressional waves; a medium. (2) OpenStax Physics, 14.1 Speed of Sound, Frequency, and Wavelength, https://openstax.org/books/physics/pages/14-1-speed-of-sound-frequency-and-wavelength : a vibrating string sends out a series of compressions (high pressure) and rarefactions (low pressure) as a sound wave; compressions and rarefactions in longitudinal waves are analogous to crests and troughs in transverse waves; wavelength. (3) Wikipedia, Longitudinal wave, https://en.wikipedia.org/wiki/Longitudinal_wave : compression and rarefaction; displacement parallel to propagation. Licence: own work

The drawing: Drawn for this site by script, 2026-09-26. Own work, nothing traced. Licence: own work

How it works

These are the parts of a longitudinal wave, drawn as a sound wave in air: a vibrating source pushes the particles into bunches and gaps that travel away from it. It works as a sound wave diagram labeled too.

Read the full guide

Bunched and spread

Where the particles are pushed together is a compression, at higher pressure. Where they are spread apart is a rarefaction, at lower pressure. The wavelength runs from one compression to the next.

Two directions

The wave travels away from the source, carrying energy. Each particle only moves back and forth along the same line as the wave, then returns to where it was.

  • Compressions and rarefactions in a longitudinal wave match the crests and troughs of a transverse wave.

Questions and answers

What is a compression in a longitudinal wave?

A region where the particles of the medium are pushed close together, so the pressure is higher. It is followed by a rarefaction, where they are spread apart.

Is sound a longitudinal wave?

Yes. A vibrating object such as a speaker or a guitar string pushes the air into compressions and rarefactions that travel out as sound.

How is wavelength measured in a longitudinal wave?

From the middle of one compression to the middle of the next, or from one rarefaction to the next: the length of one whole wave.

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