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(B) The passenger on the bus hears two sounds: the direct sound from the horn and the reflected sound from the wall.Since the bus is moving towards th

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$5$

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(B) The passenger on the bus hears two sounds: the direct sound from the horn and the reflected sound from the wall.Since the bus is moving towards the wall with velocity $v_B = 5 \ m/s$,the wall acts as a source of reflected sound.The frequency of the direct sound heard by the passenger is $n = 165 \ Hz$.The frequency of the reflected sound $(n')$ heard by the passenger is given by the Doppler effect formula for a moving observer and a stationary source (the wall acts as a stationary source reflecting the sound):$n' = n \left( \frac{v + v_B}{v - v_B} ight)$Substituting the given values ($v = 355 \ m/s$,$v_B = 5 \ m/s$,$n = 165 \ Hz$):$n' = 165 \left( \frac{355 + 5}{355 - 5} ight) = 165 \left( \frac{360}{350} ight) = 165 	imes \frac{36}{35} = 169.71 \approx 170 \ Hz$.The number of beats heard per second is the difference between the frequencies:$	ext{Beats} = n' - n = 170 \ Hz - 165 \ Hz = 5 \ Hz$.

$A$ bus is moving with a velocity of $5 \ m/s$ towards a huge wall. The driver sounds a horn of frequency $165 \ Hz$. If the speed of sound in air is $355 \ m/s$,the number of beats heard per second by a passenger on the bus will be:

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