Transverse & Longitudinal Waves (Cambridge International IGCSE Physics)

Transverse waves

Spec point — 3.1.3 · Know that for a transverse wave, the direction of vibration is at right angles to the direction of propagation and understand that electromagnetic radiation, water waves and seismic S-waves (secondary) can be modelled as transverse

• Waves can exist as one of two types:

  • Transverse
  • Longitudinal

• Transverse waves are defined as:

Waves where the direction of vibration is at right angles to the direction of propagation

• For a transverse wave, the particles of the medium vibrate perpendicular to the direction in which the wave is travelling
• Mechanical transverse waves can travel through solids and along the surface of a liquid, but not through the body of a liquid or through a gas
• Non-mechanical transverse waves can move in a vacuum

Transverse waves can be seen in a rope when it is moved quickly up and down

• Examples of waves that can be modelled as transverse are:

  • Electromagnetic waves (such as radio waves, visible light, X-rays)
  • Ripples on the surface of water
  • Seismic S-waves (secondary earthquake waves)

Longitudinal waves

Spec point — 3.1.3 · Know that for a longitudinal wave, the direction of vibration is parallel to the direction of propagation and understand that sound waves and seismic P-waves (primary) can be modelled as longitudinal

• Longitudinal waves are defined as:

Waves where the direction of vibration is parallel to the direction of propagation

• For a longitudinal wave:

  • The particles of the medium vibrate back and forth parallel to the direction in which the wave travels
  • They can move in solids, liquids and gases
  • They cannot move in a vacuum (since there are no particles)

• The key features of a longitudinal wave are:

  • Regions where the particles of the medium are close together, called compressions
  • Regions where the particles of the medium are spread apart, called rarefactions

Longitudinal waves can be seen in a slinky spring when it is moved quickly backwards and forwards

• Examples of waves that can be modelled as longitudinal waves are:

  • Sound waves
  • Seismic P-waves (primary earthquake waves)

Difference between transverse and longitudinal waves

Exam Hint Make sure you state the direction of vibration with respect to the direction of wave travel when defining transverse and longitudinal waves. Saying that a wave travels in the direction of energy transfer will not gain the mark, because this is true of every wave.

Remember that P-waves are longitudinal, while S-waves are transverse.