Physics › Section L · Sound and hearing › Topic L.3
The Doppler effect and sonic booms
An ambulance siren drops in pitch the instant it passes you, even though the siren itself never changes. Motion of the source or the listener shifts the frequency you hear, and when a source outruns its own sound the waves pile up into a sonic boom.
In this topic
- A siren that changes its tune
- Why a moving source changes the wavelength
- The two cases as formulas
- One formula and its sign convention
- Worked example: an ambulance passes
- Worked example: a car meets a train
- Doppler shifts at work
- Faster than sound: shock waves
- Sonic booms
- Worked example: where is the jet?
- Common mistakes to avoid
- Key takeaways
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