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A sound wave of frequency v travels horizontally to right. It is reflected from a large vvertical plane surface moving to the left with a speed v. The speed of sound in the medium is c, then |
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Answer» the frequency of the reflected wave is `(V(C+v))/(c-v)` `n'=((c+v))/(lambda)=(v(c+v))/(c)` Now, these waves are reflected by the moving target (Which now act as a source). THEREFORE, apparent frequency of reflected second `n''=((c)/(c-v))n'=v((c+v)/(c-v))` The wavelength of reflected wave `=(c)/(n'')=(c(c-v))/(v(c+v))` The number of beats heard by stationary listener `=n''-v=v` `((c+v)/(c-v))-v=(2"vv")/((c-v))` Hence, option (a) is correct. |
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