Reference Terms
from Wikipedia, the free encyclopedia

Doppler effect

The Doppler effect, named after Christian Andreas Doppler, is the apparent change in frequency or wavelength of a wave that is perceived by an observer moving relative to the source of the waves.

The siren on a passing emergency vehicle will start out higher than its stationary pitch, slide down as it passes, and continue lower than its stationary pitch as it recedes from the observer.

Note:   The above text is excerpted from the Wikipedia article "Doppler effect", which has been released under the GNU Free Documentation License.
Related Stories
 


Science News
May 27, 2017

Latest Headlines
updated 12:56 pm ET