A sound wave of frequency n travels horizontally to the right with speed with speed c. It is reflected from a broad wall moving to the left with speed v. The number of beats heard by a stationary observer to the left of the wall isA. zeroB. `(n(c+v))/(c-v)`C. `(nv)/(c-v)`D. `(2nv)/(c-v)`

A sound wave of frequency n travels horizontally to the right with sp

1.	A sound wave of frequency n travels horizontally to the right with speed with speed c. It is reflected from a broad wall moving to the left with speed v. The number of beats heard by a stationary observer to the left of the wall isA. zeroB. `(n(c+v))/(c-v)`C. `(nv)/(c-v)`D. `(2nv)/(c-v)`
Answer» Correct Answer - D Initially wall behaves as an approaching observer, so frequency of sound reaching the wall is `n_1=(c+v)/(c )n` while reflecting, the wall behaves as an approaching source, so frequency received by stationary observer is `n_2=(c)/(c-v)n_1=(c)/(c-v)xx(c+v)/(c)n=(c+v)/(c-v)n` Direct frequency received by observer in n. the number of beats is `x=n_2-n=(c+v)/(c-v)n-n=(2nv)/(c-v)`

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A sound wave of frequency n travels horizontally to the right with speed with speed c. It is reflected from a broad wall moving to the left with speed v. The number of beats heard by a stationary observer to the left of the wall isA. zeroB. `(n(c+v))/(c-v)`C. `(nv)/(c-v)`D. `(2nv)/(c-v)`

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