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$200$ $H_Z$
B$400$ $H_Z$
C$412$ $H_Z$
D$388$ $H_Z$
JEE MAIN 2023, Medium
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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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