3.1.1 Features of Waves

• Waves are described as oscillations or vibrations about a fixed point
• Ripples cause particles of water to oscillate up and down
• Sound waves cause particles of air to vibrate back and forth
• Waves transfer energy without transferring matter
• For water waves, the wave itself travels, not the water

  For sound waves, the wave itself travels, not the air molecules
• Objects floating on water provide evidence that waves only transfer energy and not matter
• Wave vibrations can be shown on ropes (transverse) and springs (longitudinal)
• Properties of waves: frequency, wavelength, and wave speed can be observed using water waves in a ripple tank
• The wavelength of waves can be determined by:

  • Using a ruler to measure the length of the screen
  • Dividing this distance by the number of wavefronts
• The frequency can be determined by:

  • Timing how long it takes for a given number of waves to pass a particular point
  • Dividing the number of wavefronts by the time taken
• The wave speed can be determined by using the equation wave speed = frequency × wavelength
• Important terms in wave motion include:

  • Crest
  • Trough
  • Amplitude
  • Wavelength
  • Frequency
  • Wave speed
  • Wavefront
  • Compression
  • Rarefaction
• Transverse waves are waves where the oscillations are perpendicular to wave propagation.
• Longitudinal waves are waves where oscillations are parallel to wave propagation.
• In a transverse wave, particles move up and down from their equilibrium position.
• In a longitudinal wave, particles vibrate back and forth along the direction of energy transfer.
• Sound is an example of a longitudinal wave.
• Crest is defined as the highest point on a wave above the equilibrium position.
• Trough is defined as the lowest point on a wave below the equilibrium position.
• Wavelength is defined as the distance between two consecutive points that have the same phase difference (e.g., crest-crest).
• Amplitude is the maximum or minimum displacement from the undisturbed position.
• Symbol of amplitude is A and unit of measurement is meters (m)
• Symbol of wavelength is lambda and unit of measurement is meters (m)
• Frequency is the number of waves passing through a given point per second.
• Symbol of frequency is f and unit of measurement is Hertz (Hz)
• Speed is the rate at which energy travels along the medium, measured in m/s.
• The speed of sound depends on the temperature and density of the medium.
• Wave speed = Frequency x Wavelength
• The wave equation is v=fλ where v is velocity, f is frequency, and λ is wavelength.
• Waves can be longitudinal or transverse depending on whether they compress or stretch the medium.
• Symbol of wave speed is v and unit of measurement is meter per second (m/s)
• Wavefront is the line of constant displacement of a point on a wave.
• Close wavelengths mean short wavelength.
• Far wavelength means long wavelength.
• Compression is the region in a longitudinal wave where particles are closest together.
• Rarefaction is the region in a longitudinal wave where particles are furthest apart.
• The amplitude of a transverse wave is the maximum distance from equilibrium position, while the amplitude of a longitudinal wave is the maximum compression or rarefaction.