A band playing music at a frequency `f` is moving towards a wall at a speed `v_(b)`. A motorist is following the band with a speed `v_(m)`. If `v` is the speed of sound, obtain an expression for the beat frequency heard by the motorist.

Options

A. `(v+v_(m))/(v+v_(b))f`
B. `(v+v_(m))/(v-v_(b))f`
C. `(2v_(b)(v+v_(m)))/(v^(2)-v_(b)^(2))f`
D. `(2v_(m)(v+v_(b)))/(v^(2)-v_(m)^(2))f`

Answer

C