Waves in Air, Fluids and Solids

• Waves

  Two types:
• Types of waves

  • Transverse
  • Longitudinal
• Transverse wave


  Wave for which the oscillations are perpendicular to the direction of energy transfer
• Longitudinal wave


  Wave for which the oscillations are parallel to the direction of energy transfer
• Transverse waves

  • Electromagnetic waves
  • Seismic s-waves
• Longitudinal waves

  • Sound waves
  • Seismic p-waves
• Parts of a longitudinal wave

  • Compressions
  • Rarefactions
• Wave amplitude


  The maximum displacement of a point on a wave from its undisturbed position
• Wavelength


  The distance from a point on a wave to the same position on the adjacent wave, most commonly peak to peak or trough to trough
• Wave frequency


  The number of waves that pass a given point each second
• Unit of frequency

  Hertz, Hz
• A frequency of 200Hz means 200 waves pass a given point each second
• Wave speed

  The speed at which the wave moves or at which energy is transferred through a medium
• Waves transfer energy
• Calculating wave speed

  1. Wave Speed = Frequency x Wavelength

  2. Speed (m/s), Frequency (Hz), Wavelength (m)
• Reflection

  When a wave bounces off a surface
• How sound waves travel through solids (Higher)

  The particles in the solid vibrate and transfer kinetic energy through the material
• Frequency range of human hearing (Higher)

  20 Hz - 20kHz (1kHz = 1000 Hz)
• Ultrasound waves (Higher)


  Waves which have a frequency higher than the upper limit of human hearing (20kHz)
• Uses of ultrasound waves (Higher)

  • Medical or industrial imaging
• Earthquakes cause seismic waves, which produce both P-waves and S-waves (Higher)
• Technique used to detect objects in deep water and measure water depth (Higher)

  1. Echo sounding

  2. High frequency sound waves are emitted, reflected and detected

  3. Time difference between emission and detection, alongside wave speed, are used to calculate distances