Whenever there is relative motion, what will occur?

When there is relative motion between the radar and the target, the frequency of the reflected signal changes due to the Doppler effect. This phenomenon occurs when the source of the signal (the radar) and the observer (the target) are moving relative to each other.

As the target moves towards the radar, the waves are compressed, resulting in a higher frequency of the reflected signal. Conversely, if the target is moving away from the radar, the waves are stretched, leading to a lower frequency. This shift in frequency is directly related to the speed of the target relative to the radar; hence, the frequency of the reflected signal will differ from the frequency of the transmitted signal based on the motion occurring between them.

This principle is crucial for understanding how radar systems can determine the speed and direction of objects.