JEE Main · 2023 · 08 Apr 2023 · Shift 1 · Waves & Sound

The engine of a train moving with speed

10 ms^{- 1}

towards a platform sounds a whistle at frequency 400 Hz. The frequency heard by a passenger inside the train is (neglect air speed. Speed of sound in air

330 ms^{- 1}

)

(A)200 Hz
(B)400 Hz✓ Correct
(C)412 Hz
(D)388 Hz

Answer: (B)

Solution

The passenger and the source (engine) are both moving together with the same velocity. Their relative velocity is zero, so there is no Doppler effect. The frequency heard by the passenger is the same as the source frequency, 400 Hz.

JEE Main · 2023 · 08 Apr 2023 · Shift 1 · Single correct option

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