| 释义 |
doppler effect
noun
Usage: usually capitalized D
Etymology: after C.J.Doppler
: a change in the frequency with which waves (as sound, light, or radio waves) from a given source reach an observer, the frequency decreasing with the speed at which source and observer move away from each other and increasing with the speed at which they move toward each other so that the pitch of a sound is apparently raised or lowered as the source and the observer move toward or away from each other or the spectral lines of a star are shifted toward red or violet as the star recedes or approaches the earth |