6.1 Waves in Air, Fluids and Solids

• Waves


  Two types: Transverse and Longitudinal
• Transverse wave


  Oscillations are perpendicular to the direction of energy transfer
• Longitudinal wave


  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 and rarefactions
• Wave amplitude


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


  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


  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


  Speed at which the wave moves or at which energy is transferred through a medium
• A wave transfers 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
• Seismic waves (Higher)


  Produced by earthquakes, include both P-waves and S-waves
• Difference between P-waves and S-waves (Higher)

  1. waves travel through both solids and liquids, S-waves only travel through solids (not liquids)
• Echo sounding (Higher)


  Technique used to detect objects in deep water and measure water depth, using high frequency sound waves that are emitted, reflected and detected, with time difference and wave speed used to calculate distances