A source of sound whose frequency is 1000 Hz is moving with a speed 33 m/s. The waves raflected be a fixed obstacle are registered by a receiver that moves together with the source.
The speed of the sound waves is 330 m/s, then the frequency registered by the reciver is

Options

A. 0.9 kHz
B. 1.1 kHz
C. 1.2 kHz
D. 2.2 kHz

Answer

C

Explanation

Frequency of reflected sound, `f_(1)=f((v)/(v-v_(s)))`
`=1000((330)/(330-33))=(1000xx330)/(297)`
Frequrncy observed by obsercer,
`f_(2)=f_(1)((v+v_(D))/(v))=(1000xx330)/(297)((330+33)/(330))`
`=(1000xx363)/(297)=1.2xx1000=1.2` kHz