GCSE Physics · AQA 8463 · Topic 4.6.1
Waves in air, fluids and solids
Key points
- Transverse waves: oscillations perpendicular to the direction of energy transfer. Longitudinal waves: oscillations parallel to it, with compressions and rarefactions.
- Amplitude is the maximum displacement from rest; wavelength is the distance from one point to the same point on the next wave; frequency is waves per second (Hz).
- Wave equation: . Period: .
- Waves can be reflected, absorbed or transmitted at a boundary.
- (Separate physics) The human ear hears about 20 Hz to 20 kHz. Ultrasound (above 20 kHz) is used for medical scans and echo sounding. Seismic P-waves are longitudinal and pass through solids and liquids; S-waves are transverse and cannot travel through liquids, which is evidence for Earth's liquid outer core.
- Required practical: measure the speed of water waves in a ripple tank and of waves on a string.
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Ripples on a pond, sound through a wall and the shaking from an earthquake are all mechanical waves. They pass energy along through a material while the particles themselves only vibrate about fixed positions.
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