Transverse & Longitudinal Waves (Edexcel IGCSE Physics: Double Science)

• Waves can come in one of two types:
  • Transverse waves
  • Longitudinal waves

Transverse waves

• Transverse waves are defined as:

Waves that vibrate or oscillate perpendicular to the direction of energy transfer

• Transverse waves:
  • oscillate perpendicularly to the direction of travel
  • transfer energy, but not the particles of the medium
  • exist as mechanical waves which can travel in solids and on the surfaces of liquids but not through liquids or gases
  • exist as electromagnetic waves which can move in solids, liquids, gases and in a vacuum

• On a transverse wave:
  • the highest point above the rest position is called a peak, or crest
  • the lowest point below the rest position is called a trough

Example of a transverse wave

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

• Examples of transverse waves are:
  • Ripples on the surface of water
  • Vibrations in a guitar string
  • S-waves (a type of seismic wave)
  • Electromagnetic waves (such as radio, light, X-rays etc)

Longitudinal waves

• Longitudinal waves are defined as:

Waves where the points along its length vibrate parallel to the direction of energy transfer

• Longitudinal waves:

  • Oscillate in the same direction as the direction of wave travel

  • Transfer energy, but not the particles of the medium

  • Move in solids, liquids and gases

  • Cannot move in a vacuum (since there are no particles)

• The key features of a longitudinal wave are where the points are:
  • Close together, called compressions
  • Spaced apart, called rarefactions

Example of a longitudinal wave

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

• Examples of longitudinal waves are:
  • Sound waves
  • P-waves (a type of seismic wave)
  • Pressure waves caused by repeated movements in a liquid or gas

Comparing transverse & longitudinal waves

• Wave vibrations can be shown on ropes (transverse) and springs (longitudinal)

A comparison of longitudinal and transverse waves

Waves can be shown through vibrations in ropes or springs

Properties of transverse and longitudinal waves

• Waves are disturbances caused by an oscillating source that transfer energy and information without transferring matter

• Waves are described as oscillations or vibrations about a fixed point
  • For example, ripples cause particles of water to oscillate up and down
  • Sound waves cause particles of air to vibrate back and forth

Evidence that waves transfer energy and not matter

Waves transfer energy and information, but not matter. This toy duck bobs up and down as water waves pass underneath

• The wave on the surface of a body of water is a transverse wave
• The duck moves perpendicular to the direction of the wave
  • The duck moves up and down but does not travel with the wave