A bus is moving with a velocity of 5 ,m/s tow | vedclass

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(B) The frequency of the sound heard by the wall (which acts as a stationary observer) is given by $f' = f \left( \frac{v}{v - v_s} \right)$, where $v

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$5$

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(B) The frequency of the sound heard by the wall (which acts as a stationary observer) is given by $f' = f \left( \frac{v}{v - v_s} ight)$, where $v = 335 \,m/s$ and $v_s = 5 \,m/s$.$f' = 165 \left( \frac{335}{335 - 5} ight) = 165 \left( \frac{335}{330} ight) = 165 	imes \frac{335}{330} = \frac{335}{2} = 167.5 \,Hz$.Now, the wall acts as a source reflecting this sound back to the bus (which acts as a moving observer). The frequency $f''$ heard by the passengers is $f'' = f' \left( \frac{v + v_o}{v} ight)$, where $v_o = 5 \,m/s$.$f'' = 167.5 \left( \frac{335 + 5}{335} ight) = 167.5 \left( \frac{340}{335} ight) = 167.5 	imes \frac{340}{335} = 167.5 	imes 1.0149 \approx 170 \,Hz$.The number of beats per second is the difference between the reflected frequency and the original frequency: $f_{beats} = f'' - f = 170 \,Hz - 165 \,Hz = 5 \,Hz$.

$A$ bus is moving with a velocity of $5 \,m/s$ towards a wall. The driver blows the horn of frequency $165 \,Hz$. If the speed of sound in air is $335 \,m/s$, then after reflection of sound wave, the number of beats per second heard by the passengers in the bus will be

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