Waves introduction

• Waves transfer energy and information without transferring matter.

  Evidence of this for a water wave can be seen when a ball dropped into a pond bobs up and down , but the wave energy travels outwards as ripples across the surface of the pond.
• Waves can be described by their:

  • Frequency - number of waves passing a point each second , measured in hertz ( Hz)
  • Speed - measured in meters per second ( m/s )
  • Wavelength
  • Amplitude
  • Period - in s = 1 / frequency in Hz
• Longitudinal waves

  Examples are:

  • Sound waves
  • Seismic P waves

  The particles in the material through which sound is travelling move back and forth along the same direction that sound is travelling.

  -

  Particles in a LONGtudinal wave move aLONG the same direction as the wave.
• Transverse waves:

  Ripples on the surface of water

  -

  Examples are:

  • Electromagnetic waves
  • Seismic S waves

  -

  The particles of water move in a direction at right angles
• Typical values for waves

  Velocity m/s | Frequency Hz | Wavelength m

  Sound | - 340 ————————- 3000 —————- 0.11 —————-

  Water | —- 5 —————————— 5 ———————- 1—————

  Light | 300000000 ——— 6 x 10 14 ——————- 5 x 10 -7

  S wave | 4000 —————- 40 ————————— 100 ———