Doppler Effect

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What Does Doppler Effect Mean?

The Doppler effect is a phenomenon related to the effects of moving objects on an electromagnetic field. In this, an observer in relative motion to a wave experiences a change in the frequency or wavelength of the wave. For example, consider a person standing near a road. A honking vehicle approaches the observer, nears and then recedes from the observer. While the vehicle is approaching, the observer hears the horn as a low tone. However, as the vehicle nears the observer, the sound becomes higher and higher pitched and is the highest at the closest point to the person. But after passing that point, the frequency or the pitch of the sound lowers with distance.


The Doppler effect is also known as Doppler shift.

Techopedia Explains Doppler Effect

The Doppler effect is a very
common phenomenon occurring in everyday life. It is not just limited to
electromagnetic waves. Objects producing waves of any kind can create the
phenomena of the Doppler effect. In this phenomenon, a wave source passes from near
an observer in relative motion to the object. As it closes in toward the
observer, a crest of the wave is generated from a point closer to the observer
than the previous one. In this way, the time of arrival to the user is reduced,
along with the distance between each wave. This results in an increase of frequency
while the object is moving toward the observer. On the other hand, the
converse of this process occurs when the object is moving away from the
observer. The distance between the waves is increased as the waves spread out and disperse, and the frequency of the wave is reduced.

This effect was named after Christian Doppler of Austria, who proposed this phenomenon in 1842.


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Margaret Rouse
Technology Expert
Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.