A sound wave of frequency `f` travels horizontally to the right . It is teflected from a larger vertical plane surface moving to left with a speed `v`. the speed of sound in medium is `c`
(a) The number of waves striking the surface per second is `f(c + upsilon)/(c)`
(b) The wavelength of reflected wave is `(c(c-upsilon))/(f(c+upsilon))`
(c) The frequency of the reflected wave is ` f((c+upsilon))/((c+upsilon))`
(d) The number of beats heard by a stationary listener to the left of the reflecting surface is `(upsilon f)/(c - upsilon)`

Options

A. The number of waves striking the surface per second is `f((c+v))/(c)`
B. The wavelength of reflected wave is `(c(c-v))/(f(c+v))`
C. The frequeency of the reflected wave is `f((c+v))/((c-v))`
D. The number of beats heard by a stationary listener to the left of the reflecting surface is `(vf)/(c-v)`

Answer

A, B, C, D

Explanation

Moving plane is like a moving observer,Therefore number of waves encounntered by moving plane
`f_1=f((v+v_0)/(c))=f((c+v)/(c))`
Frequency of reflected wave, `f_2=f_1((v)/(v-v_0))=f((c+v)/(c-v))`
Wavelength of reflected wave, `lambda_2=(v)/(f_2)=(c)/(f_2)=c/(f)((c-v)/(c+v))`
Number of beats heard`=f_2-f=(2vf)/(c-v)`