Doppler effect
Velocity changes pitch
The Doppler effect is the change in frequency of a wave as the source and observer move toward or away from each other.
When an ambulance approaches, its siren sounds higher-pitched; as it passes and recedes, the pitch drops noticeably lower.
This phenomenon applies to all waves, including sound and light.
In astronomy, the Doppler effect reveals whether celestial objects are moving toward or away from Earth by shifts in their light spectrum toward blue or red.
- blueshiftedWavelength decreased by approach
- redshiftedWavelength increased by motion
- wavelengthSpatial repetition interval
- frequencyRate of recurrence
- recedingMoving away from observer
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