Doppler effect is the change in perceived pitch caused by the relative motion between what two elements?

Doppler effect is the change in perceived pitch caused by the relative motion between what two elements?

• A. The light source and the observer
• B. The sound source and the observer
• C. The circuit and the conductor
• D. The observer and the medium

Answer: (B)

The Doppler effect describes how the pitch you hear changes when the source of the sound and the listener move relative to each other. When the source moves toward you, its wavefronts bunch up, so you encounter more waves per second and the pitch sounds higher. When the source moves away, the wavefronts spread out, you encounter fewer waves per second, and the pitch sounds lower. The same idea applies if you move toward or away from the source—the perceived frequency changes because of the changing rate at which you meet successive wavefronts. So the effect centers on the relative motion between the sound source and the observer and how that changes the frequency of the waves reaching your ears. The other options don’t capture the cause in this standard sense: the circuit or conductor is unrelated to sound waves; moving the observer relative to the medium alone isn’t what sets the Doppler shift for sound in everyday scenarios; and for light, the Doppler shift is a different, relativistic consideration.

The Doppler effect describes how the pitch you hear changes when the source of the sound and the listener move relative to each other. When the source moves toward you, its wavefronts bunch up, so you encounter more waves per second and the pitch sounds higher. When the source moves away, the wavefronts spread out, you encounter fewer waves per second, and the pitch sounds lower. The same idea applies if you move toward or away from the source—the perceived frequency changes because of the changing rate at which you meet successive wavefronts.

So the effect centers on the relative motion between the sound source and the observer and how that changes the frequency of the waves reaching your ears. The other options don’t capture the cause in this standard sense: the circuit or conductor is unrelated to sound waves; moving the observer relative to the medium alone isn’t what sets the Doppler shift for sound in everyday scenarios; and for light, the Doppler shift is a different, relativistic consideration.