Question

A boy riding on a bicycle going at 12 km $h^{-1}$ towards a vertical wall whistles at his dog on the ground. If the frequency of the whistle is 1600 Hz and the speed of sound in air is $330m{s}^{-1}$, find (a) the frequency of the whistle as received by the wall (b) the frequency of the reflected whistle as received by the boy.

Answer 1

Required frequency,

$n=\frac{v+v_0}{v-v_s}\times n_0.$

$=\frac{330+0}{330-\frac{10}{3}}\times 1600=1616Hz$

(b)Required frequency,

$n=\frac{v+v_0}{v+v_s}\times n_0$

$=\frac{330+\frac{10}{3}}{330+0}\times 1616=1632Hz$