Definition of Doppler effect in US English:

Doppler effect


  • An increase (or decrease) in the frequency of sound, light, or other waves as the source and observer move toward (or away from) each other. The effect causes the sudden change in pitch noticeable in a passing siren, as well as the redshift seen by astronomers.

    • ‘There is a familiar analogous phenomenon for sound known as the Doppler effect, which explains, for instance, why the pitch of an oncoming train changes as the train approaches and then recedes from us.’
    • ‘The normal Doppler effect causes sound waves to get longer if the source of the sound is moving away - for example, a receding ambulance siren.’
    • ‘In the astronomical setting, the Doppler effect applies to light.’
    • ‘This determination assumes the variation of the redshift is indeed a Doppler effect due to motion of the star.’
    • ‘Basically the Doppler effect is that pitch increases the closer something gets to you, and it decreases the further away it gets.’


Doppler effect

/ˈdɑplər əˌfɛkt/