What phenomenon occurs when a Doppler effect leads to different measurements of wave frequencies?

The phenomenon that occurs with the Doppler effect, which leads to different measurements of wave frequencies, is indeed the result of how the relative motion between the source of the waves and the observer affects the perceived frequency and wavelength. When a wave source moves toward an observer, the waves are compressed, leading to a higher frequency (and shorter wavelength), while if the source moves away, the waves are stretched, resulting in a lower frequency (and longer wavelength).

This effect is fundamental in various applications, including speed detection in law enforcement. For instance, when a police radar gun detects the speed of a vehicle, it utilizes the Doppler effect to determine changes in frequency. The correct identification of this phenomenon lies in understanding how motion alters our perception of wave frequencies, thereby causing a variance in measurements based on the direction and speed of the source relative to the observer.

Shadowing, reflection, refraction, and absorption each describe different aspects of wave interaction but do not specifically pertain to the changes in frequency measurements caused by motion, which is aptly described by the Doppler effect.