A sonic source of requency `n_(0)=272Hz` is moving along a horizontal circle of radius `R=3m` with a speed `u=10ms^(-1)`. A stationary receiver lies in the same plane at distance d=5m from centre of the circle. Speed of sound in air is `v=330ms^(-1)`.

Options

A. minimum frequency received by the receiver is 264 Hz
B. minimum frequency received by the receiver is 272 Hz
C. If at t=0, receiver receives minimum frequency, the minimum value of time t when it receives maximum frequency is `(127)/(300)pi` sec.
D. sound wave pulse emitted by source at points A and C will be received as with their actual frequency i.e, 272 Hz

Answer

A, C, D

Explanation

`n_("min")=n_(0)((v+0)/(v-(v_(S))))=272((330)/(330+10))=264Hz`
In `DeltaOER`,
`costheta=(3)/(5)" "therefore theta=53^(@)=(53pi)/(180)rad`
Pulse emitted from position E will be received as min frequency pulse annd pulse emitted at F will be received as maximum frequency pulse.

`therefore`Time gap between minimum and next max. frequency received=time taken by source to move from E to F.
`=((2pi-(2xx53pi)/(180))xx3)/(10)=(127pi)/(300)sec`
When source is at point A and C, source velocity is perpendicular to the line joining source and observer.
`therefore`Frequency of pulse emitted from position A and C are when received
`therefore f_("apparent")=f_("actual")((V+V_(0))/(V-V_(S)))=f_("actual")" "(V_(S)=0,V_(0)=0)`