Sound Waves (CIE IGCSE Physics)

• Sound waves are produced by vibrating sources
• When a sound wave comes into contact with a solid, those vibrations can be transferred to the solid
  • For example, sound waves can cause a drinking glass to vibrate
  • If the glass vibrates too much the movement causes the glass to shatter

Sound waves are longitudinal: the molecules vibrate in the same direction as the energy transfer

• Sound waves require a medium to travel through
  • This means that if there are no molecules, such as in a vacuum, then the sound can’t travel through it

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• Longitudinal waves consist of compression and rarefactions:
  • A compression is a region of higher density i.e. a place where the molecules are bunched together
  • A rarefaction is a region of lower density i.e. a place where the molecules are spread out

Sound is a longitudinal wave consisting of compressions and rarefactions - these are areas where the pressure of the air varies with the wave

• These compressions and rarefactions cause changes in pressure, which vary in time with the wave
  • Therefore, sound is a type of pressure wave

• When the waves hit a solid, the variations in pressure cause the surface of the solid to vibrate in sync with the sound wave

When sound waves hit a solid, the fluctuating pressure causes the solid to vibrate