Effective change of frequency of a received signal due to the relative velocity of transmitter with respect to a receiver describes which propagation effect?

The correct answer is the Doppler shift, which refers to the change in frequency (or wavelength) of a wave in relation to an observer moving relative to the wave source. This phenomenon occurs in various types of wave propagation, including sound and electromagnetic waves.

When there is relative motion between the transmitter and the receiver, the frequency of the received signal alters depending on whether the transmitter is moving towards or away from the receiver. If the transmitter moves closer, the frequency appears to increase; if it moves away, the frequency appears to decrease. The Doppler effect is widely exploited in numerous applications, such as radar and sonar, to determine the velocity of moving objects.

Other options like destructive interference, reflection, and refraction involve different wave behaviors. Destructive interference relates to the combined effects of waves canceling each other out, reflection pertains to waves bouncing off surfaces, and refraction involves the bending of waves as they pass through different mediums. While these phenomena are significant in the study of wave properties, they do not specifically describe the effect of relative motion on signal frequency.