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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 )

1. 400 Hz
2. 200 Hz
3. 412 Hz
4. 388 Hz

Correct answer: 400 Hz

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