Glossary Definition

What is the Doppler Effect?

The Doppler effect, or Doppler shift, describes the changes in frequency of any kind of sound or light wave produced by a moving source with respect to an observer.
Waves emitted by an object traveling toward an observer get compressed — prompting a higher frequency — as the source approaches the observer.
In contrast, waves emitted by a source traveling away from an observer get stretched out — prompting a lower frequency.

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