Which effect explains the change in perceived frequency when the source moves relative to the observer?

Which effect explains the change in perceived frequency when the source moves relative to the observer?

• A. Doppler effect
• B. Echo
• C. Interference
• D. Diffraction

Answer: (A)

The change in perceived frequency when the source moves relative to the observer is explained by the Doppler effect. When the source approaches, waves are emitted more closely together in the observer’s frame, raising the observed frequency (higher pitch); when it moves away, waves are emitted farther apart, lowering the observed frequency (lower pitch). For sound, this depends on the speed of sound in the medium (like air). Echo is simply a reflected sound causing a delayed duplicate; interference involves the combining of waves to produce patterns of loud and soft regions; diffraction is the bending of waves around obstacles or through openings. The Doppler effect uniquely accounts for how relative motion shifts frequency, which is why it’s the correct explanation.

The change in perceived frequency when the source moves relative to the observer is explained by the Doppler effect. When the source approaches, waves are emitted more closely together in the observer’s frame, raising the observed frequency (higher pitch); when it moves away, waves are emitted farther apart, lowering the observed frequency (lower pitch). For sound, this depends on the speed of sound in the medium (like air). Echo is simply a reflected sound causing a delayed duplicate; interference involves the combining of waves to produce patterns of loud and soft regions; diffraction is the bending of waves around obstacles or through openings. The Doppler effect uniquely accounts for how relative motion shifts frequency, which is why it’s the correct explanation.