ATPL EASA Radio Navigation Practice Exam 2025 – Complete Test Prep

The characteristic that applies to both the Doppler effect and Doppler shift is their association with relative motion and frequency changes.

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. This phenomenon is commonly observed in sound waves, such as the changing pitch of an ambulance siren as it approaches and then moves away from an observer. The frequency increases when the source moves closer and decreases as it moves away, demonstrating how relative motion affects frequency.

Doppler shift is essentially the measurement of this change in frequency. It quantifies the difference between the emitted frequency by the source and the frequency observed by the receiver as a result of their relative motion.

Hence, both concepts fundamentally rely on the principles of relative motion and the resulting changes in frequency, making this option the correct choice. The other options, while they touch on wave phenomena, do not accurately reflect the core principles of the Doppler effect and Doppler shift, which are centered on frequency modulation resulting from motion.