An autorickshaw with horn at frequency $f_0$ moves toward a stationary listener. The listener hears a frequency:
AHigher than $f_0$, since the source approaches
BLower than $f_0$, since the source moves at all
CEqual to $f_0$, since only observer motion shifts pitch
DZero, since the listener stands still on the road
Answer & Solution
Correct answer: A. Higher than $f_0$, since the source approaches
Approaching source compresses wavelengths; perceived frequency rises above $f_0$.
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