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Sound Waves (CIE IGCSE Physics: Co-ordinated Sciences (Double Award))
Revision Note
Describing sound
- Sound waves are produced by vibrating sources
- A medium is needed to transmit sound waves
- This means if there are no molecules, such as in a vacuum, then the sound can’t travel through it
- When a sound wave comes into contact with a solid, the wave vibrations are 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
Compression & rarefaction
Extended tier only
- Sound waves are Longitudinal waves
- Longitudinal waves travel in air as a series of compressions and rarefactions:
- Compressions are regions of higher pressure due to particles being closer together
- Rarefactions are regions of of lower pressure due to particles being spaced further apart
Compression and rarefaction
Sound is a longitudinal wave consisting of compressions and rarefactions - these are areas where the pressure of the air in the pipe varies with the wave
Exam Tip
When describing compressions and rarefactions, make sure to use the correct terms. It is best to refer to them as regions of high and low pressures of particles instead of the particles being more 'bunched up' or 'far apart', as this is too vague and not very scientific!
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