Consider a source of sound `S` and an observer `P`. The sound source is of frequency `n_0`. The frequency observed be `P` is found to be `n_1` if `P` approaches `S` at speed `v` and `S` is stationary, `n_2` If `S` approaches `P` at a speed `v` and `P` is stationary and `n_3` if each of `P` and `S` has speed `(v)/(2)` towards one another Now.

Options

A. `f_1nef_2nef_3`
B. `f_1ltf_2`
C. `f_3ltf_0`
D. `f_1ltf_3ltf_2`

Answer

B

Explanation

Let relative velocity of `v` and the speed of sound be `v_0`. Then,
`f_1=(v_0-(-v))/(v_0)xxf_0=(v_0+v)/(v_0)f_0`
`f_2=(v_0)/(v_0-v)xxf_0`
`f_3=(v_0+(v)/(2))/(v_0-(v)/(2))xxf_0`
It is clear from above that `f_1nef_2nef_3`,`f_3gtf_0` and we can prove that `f_2gtf_3gtf_1`.