A person observes two moving trains, '$A$' reaching the station and '$B$' leaving the station with equal speed of $30\,m / s$. If both trains emit sounds with frequency $300\,Hz$, (Speed of sound : $330\,m / s$ ) approximate difference of frequencies heard by the person will be $..........Hz$
JEE MAIN 2023, Medium
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$f _1=300\left(\frac{330-0}{330-(-30)}\right)=275$
$f _2=300\left(\frac{330-0}{330-(30)}\right)=330$
$\Delta f =330-275=55\,Hz$
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