Q100 / 100 · BITSAT 2023 (Memory Based Paper 2) · Physics

The engine of a train moving with speed $10 \mathrm{~ms}^{-1}$ towards a platform sounds a whistle at frequency $400 \mathrm{~Hz}$. The frequency heard by a passenger inside the train is (neglect air speed. Speed of sound in air $330 \mathrm{~ms}^{-1}$ )

  • A
    $200 \mathrm{~Hz}$
  • Correct answer
    B
    $400 \mathrm{~Hz}$
  • C
    $412 \mathrm{~Hz}$
  • D
    $388 \mathrm{~Hz}$

Solution

The relative velocity of a passenger with respect to source of sound (engine of train) is 0 . So there will be no Doppler's effect. So frequency heard is $400 \mathrm{~Hz}$.

Hence, the correct answer is option: 'B'.

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