A source of sound with natural frequency `f_0=1800Hz` moves uniformly along a straight line separated from a stationary observer by a distance `l=250m`. The velocity of the source is equal to `eta=0.80` fraction of the velocity of the sound.
Q. Find the frequency of osund received by the observer at the moment when the source gets closest to him.

Answer

5

Explanation

`costheta=(V_(x)t)/(Ct)=0.8`
`f=f[(C)/(C-V_(S)costheta)]=1.8[(C)/(C-0.8Ccostheta)]`
`=1.8(1)/(1-0.8^(2))=1.8(1)/(1-0.64)=(1.8)/(0.36)`
`=(180)/(36)=5kHz`