A siren emitting sound of frequency `800 Hz ` is going away from a static listener with a speed of 30 m/s. Frequency of the sound to be heard by the listener is ( Take velocity of sound as 300 m/s )

Options

A. 727.3 Hz
B. 481.2 Hz
C. 644.8 Hz
D. 286.5 Hz

Answer

A

Explanation

Here, `upsilon = 800 Hz, v_(s)=30 m//s, v = 300 m//s`. As the source is going away from the stationary observer, therefore.
`upsilon'=(v xx upsilon)/(v+v_(s))=(300xx800)/(300+30)=(300xx800)/(330)=727.3 Hz`.