Transverse & Longitudinal Waves (CIE AS Physics)

• In mechanical waves, particles oscillate about fixed points
• The direction of oscillation relative to the direction of wave travel determines the type of wave it is

Transverse waves

• A transverse wave is one where the particles oscillate perpendicular to the direction of the wave travel (and energy transfer)
• Transverse waves show areas of crests (peaks) and troughs

Crests and Troughs of a Transverse Wave

Diagram of a transverse wave

• Examples of transverse waves are:
  • Electromagnetic waves e.g. radio, visible light, UV
  • Vibrations on a guitar string

• These can be shown on a rope
• Transverse waves can be polarised

Longitudinal waves

• A longitudinal wave is one where the particles oscillate parallel to the direction of the wave travel (and energy transfer)
• Longitudinal waves show areas of compressions and rarefactions

Rarefactions and Compressions of a Longitudinal Wave

Diagram of a longitudinal wave

• Examples of longitudinal waves are:
  • Sound waves
  • Ultrasound waves

• These can be shown on a slinky spring
• Longitudinal waves cannot be polarised
• The diagram below shows the equivalent of a wavelength on a longitudinal wave

Comparing Wavelengths of Longitudinal and Transverse Waves

Wavelength shown on a longitudinal wave

• Transverse and longitudinal waves can be represented graphically in the same way
• The main difference is the meaning of 'displacement' on the y-axis
  • Alternatively, displacement could be exchanged for velocity or acceleration

• For a transverse wave:
  • Displacement is perpendicular to the direction of propagation (energy transfer)

• For a longitudinal wave:
  • Displacement is parallel to the direction of propagation (energy transfer)

Graphical Representation of a Progressive Wave

The wave has a period of 1.0 s, a frequency of 1.0 Hz and could be either transverse or longitudinal.