Which of the following best describes the Doppler effect in radar operation?

The Doppler effect refers to the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source. In the context of radar operation, the Doppler effect is crucial as it allows radar systems to determine the speed and direction of a target. When a radar signal is transmitted to a moving object, such as a vehicle, the frequency of the returning signal changes depending on whether the object is moving towards or away from the radar source.

If the target is approaching, the frequency increases, resulting in a "blue shift," while if the target is receding, the frequency decreases, leading to a "red shift." This shift in frequency is precisely what allows radar operators to measure the velocity of moving targets accurately, making option B the best description of the Doppler effect in radar operation.

Other options may describe relevant radar functions but do not capture the essence of the Doppler effect. For instance, adjusting radar frequency pertains to technical adjustments but does not define the Doppler effect itself. Estimating distance typically relies on time delay rather than frequency changes, and detecting multiple targets does not inherently involve frequency shifts but rather requires distinguishing between signals. Thus, the key characteristic of the Doppler effect being a shift