Doppler effect

UK: /ˈdɒplə/ US: (dop′lər)

WordReference Random House Unabridged Dictionary of American English © 2026

Dop′pler effect′  (dop′lər), [Physics.]

1. Physics (often l.c.) the shift in frequency (Dop′pler shift′)of acoustic or electromagnetic radiation emitted by a source moving relative to an observer as perceived by the observer: the shift is to higher frequencies when the source approaches and to lower frequencies when it recedes.

• named after C. J. Doppler (1803–53), Austrian physicist 1900–05

Collins Concise English Dictionary © HarperCollins Publishers::

Doppler effect / ˈdɒplə/ noun

1. a phenomenon, observed for sound waves and electromagnetic radiation, characterized by a change in the apparent frequency of a wave as a result of relative motion between the observer and the source
   Also called: Doppler shift

Etymology: 19th Century: named after C. J. Doppler (1803–53), Austrian physicist