A sound wave of frequency nu travels horizont | vedclass

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(D) $1$. The number of waves striking the surface per second (frequency of waves reaching the moving target) is given by $n' = \frac{c + v}{\lambda} =

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All of the above.

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(D) $1$. The number of waves striking the surface per second (frequency of waves reaching the moving target) is given by $n' = \frac{c + v}{\lambda} = \frac{
u (c + v)}{c}$. Thus,option $(c)$ is correct.$2$. The moving target acts as a source for the reflected waves. The apparent frequency $n''$ of the reflected wave is given by the Doppler effect formula for a moving source: $n'' = n' \left( \frac{c}{c - v} ight) = 
u \left( \frac{c + v}{c} ight) \left( \frac{c}{c - v} ight) = 
u \left( \frac{c + v}{c - v} ight)$. Thus,option $(a)$ is correct.$3$. The wavelength $\lambda'$ of the reflected wave is $\lambda' = \frac{c}{n''} = \frac{c}{
u \left( \frac{c + v}{c - v} ight)} = \frac{c(c - v)}{
u (c + v)}$. Thus,option $(b)$ is correct.$4$. Since $(a)$,$(b)$,and $(c)$ are all correct,the correct choice is $(d)$.

$A$ sound wave of frequency $\nu$ travels horizontally to the right. It is reflected from a large vertical plane surface moving to the left with a speed $v$. The speed of sound in the medium is $c$. Then:

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