An engine moving away from a vertical cliff blows a born at a frequency f. Its speed is 0.5% of the speed of sound in air. The frequency of the reflected sound received at the engine is

Options

A. 0.990f
B. 0.995f
C. 1.005f
D. 1.010f

Answer

A

Explanation

`f_(1)=f[(v)/(v+v_(s))]`
`implies f_(R)=f_(1)[(v-v_(s))/(v)]=f_(0)[(v-v_(s))/(v+v_(s))]`
`implies f_(R)=f[(1-v_(s)//v)/(1+v_(s)//v)]=f[(1-0.005)/(1+0.005)]=0.990f`.