A person observes two moving trains,A reachin | vedclass

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(B) The apparent frequency $f'$ heard by an observer is given by the Doppler effect formula: $f' = f_0 \left( \frac{v \pm v_o}{v \mp v_s} \right)$.Her

Vedclass · Accepted Answer

$55$

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(B) The apparent frequency $f'$ heard by an observer is given by the Doppler effect formula: $f' = f_0 \left( \frac{v \pm v_o}{v \mp v_s} \right)$.Here,$v = 330\,m/s$ (speed of sound),$v_o = 0$ (observer is stationary),$v_s = 30\,m/s$ (speed of source),and $f_0 = 300\,Hz$.For train $A$ (approaching the station/observer),the source is moving towards the observer: $f_A = 300 \left( \frac{330}{330 - 30} \right) = 300 \left( \frac{330}{300} \right) = 330\,Hz$.For train $B$ (leaving the station/observer),the source is moving away from the observer: $f_B = 300 \left( \frac{330}{330 + 30} \right) = 300 \left( \frac{330}{360} \right) = 300 \left( \frac{11}{12} \right) = 275\,Hz$.The difference in frequencies heard is $\Delta f = f_A - f_B = 330 - 275 = 55\,Hz$.

$A$ 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 : $330\,m/s$) the approximate difference of frequencies heard by the person will be $..........Hz$.

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