North Carolina RADAR State Practice Exam

When an object is moving away from a radar, the reflected signal frequency decreases due to the Doppler effect. The Doppler effect describes how the frequency of a wave changes for an observer moving relative to the source of the waves. In this case, as the object moves away from the radar, the waves are stretched, leading to a decrease in frequency. This results in a lower frequency signal being reflected back to the radar system compared to the original emitted signal.

Understanding this concept is critical, as it impacts how radar systems interpret the motion of objects. By measuring the frequency shift, radar can determine the speed and direction of the moving object. The other options do not accurately reflect the physics of wave behavior in relation to relative motion: frequency does not remain unchanged, it does not increase, and it does not fluctuate in a mere consistent motion away from the radar.