A train blowing a whistle of frequency $320\,Hz$ approaches an observer standing on the platform at a speed of $66\,m / s$. The frequency observed by the observer will be (given speed of sound $=330\,ms ^{-1}$ ) $.............Hz$.
JEE MAIN 2023, Easy
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$f_{a p p}=f\left(\frac{v}{v-v_s}\right)$
$=320\left(\frac{330}{330-66}\right)$
$=400\,Hz$
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