A person observes two moving trains. Train A | vedclass

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

Vedclass · Accepted Answer

$55$

Vedclass · Answer

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

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