What's Doppler Shift

Doppler shift, also known as the Doppler effect, is a change in frequency or wavelength of a wave that occurs when the source of the wave is in motion relative to the observer.

The Doppler effect can be observed in a variety of waves, including sound waves, light waves, and radio waves. When a wave source is moving towards an observer, the frequency of the wave appears to increase, resulting in a higher pitch or higher frequency. Conversely, when a wave source is moving away from an observer, the frequency of the wave appears to decrease, resulting in a lower pitch or lower frequency.

In the context of radar and sonar systems, the Doppler effect is used to measure the speed and direction of moving objects. When a radar or sonar system emits a signal towards a moving object, the frequency of the returned signal is shifted due to the Doppler effect. By analyzing the frequency shift of the returned signal, the system can determine the speed and direction of the object.

The Doppler effect is also used in a variety of other applications, including medical imaging, astronomy, and remote sensing. In medical imaging, Doppler ultrasound is used to measure blood flow in the body by detecting changes in the frequency of reflected sound waves. In astronomy, the Doppler effect is used to measure the speed and distance of stars and galaxies based on the frequency shift of their light waves.