Doppler effect
Article
The Doppler effect is the change in observed frequency caused by relative motion between a wave source and an observer. Approaching motion generally increases the observed frequency, while receding motion lowers it.
For sound, the effect depends on motion relative to the medium through which the sound travels. A moving ambulance siren therefore sounds higher in pitch as it approaches and lower after it passes.
For light and other electromagnetic waves, the relativistic Doppler effect depends on the relative motion of source and observer without requiring a material medium. Motion away produces redshift and motion toward produces blueshift.
Doppler measurements are used in radar, medical ultrasound, astronomy, weather observation, navigation, and flow measurement. They reveal the speed of vehicles, blood, stars, galaxies, winds, precipitation, and many other moving targets.
Source details and credits
- Source / publisher: Wikipedia
- URL type: WWW
- Credits: Wikipedia
- URL: https://en.wikipedia.org/wiki/Doppler_effect