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14. waves and sound — Physics STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 SciencePhysics14. waves and sound1 Mark
MCQ
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 $........\,Hz$ (neglect air speed. Speed of sound in air $330\,ms ^{-1}$ )
  • A
    $200$ $H_Z$
  • ✓
    $400$ $H_Z$
  • C
    $412$ $H_Z$
  • D
    $388$ $H_Z$
✓

Answer

Correct option: B.
$400$ $H_Z$
b
The relative velocity of a passenger with source of sound (engine) is $0$. So there will be no doppler's effect. So frequency heard is $400\,Hz$.

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