Which phenomenon explains the change in frequency of a wave in relation to an observer moving relative to the source of the wave?

The phenomenon that accurately describes the change in frequency of a wave observed when there is relative motion between the observer and the source of the wave is known as the Doppler Shift. This effect occurs whether the source of the waves is moving toward or away from the observer.

When the source of a wave, such as sound or light, moves closer to the observer, the waves are compressed, resulting in a higher frequency, which is perceived as a higher pitch in sound or a shift to the blue end of the spectrum in light. Conversely, if the source is moving away, the waves are stretched, leading to a lower frequency, perceived as a lower pitch in sound or a shift to the red end of the spectrum in light.

Understanding the Doppler Shift is crucial in various applications, including astronomy, where it helps determine the movement of celestial bodies, and in radar and satellite technologies, where it enhances the detection of moving objects. This principle illustrates how the perception of waves is not solely about their inherent properties but is also influenced by the relative motion of the source and the observer.