Two vehicles, each moving with speed `u` on the same horizontal straight road, are approaching each other. Wind blows along the road with velocity `w`. One of these vehicles blows a whistle of frequency `f_(1)`. An observer in the other vehicle hears the frequency of the whistle to be `f_(2)`. the speed of sound in still air is `V_C`. The correct statement `(s)` is (are)

Options

A. If the wind blows from the source to the observer, `f_2 gt f_1`
B. If the wind blows from the observer to the source, `f_2 gt f_1`
C. If the wind blows from observer to the source, `f_2 lt f_1`
D. If the wind blows from the source to the observer, `f_2 lt f_1`

Answer

A, B

Explanation

If wind blows from source to observer
`f_(2)=f_(1)((V+w+u)/(V+w-u))`
When wind blows from observer towards source
`f_(2) =f_(1) ((V-w+u)/(V-w-u))`
In both cases, `f_(2) gt g_(1)`.