Which principle does continuous wave operation in radar use to detect fast-moving targets?

Continuous wave operation in radar leverages the Doppler effect to detect fast-moving targets. The Doppler effect refers to the change in frequency or wavelength of a wave in relation to an observer moving relative to the source of the wave. When a target moves towards the radar source, the reflected waves are compressed, increasing their frequency. Conversely, if the target is moving away, the reflected waves are elongated, decreasing their frequency.

This frequency shift is critical for radar systems because it allows the detection of speed and direction of fast-moving targets. By processing these frequency changes, radar systems can determine not only if a target is present but also how quickly it is moving towards or away from the radar source. This principle is fundamental in applications such as air traffic control and missile guidance, where understanding the velocity of targets is crucial for operational effectiveness.

Other options refer to concepts that are important in different contexts. The inverse square law relates to the intensity of waves and how it decreases with distance, which is not directly related to detecting the speed of moving targets. Fresnel diffraction involves the bending of waves around obstacles, impacting wave propagation but not directly aiding in speed detection. Wave interference describes the phenomenon where two waves superimpose, leading to a pattern of constructive and