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 330 m/s)

(1) 733.3 Hz

(2) 644.8 Hz

(3) 481.2 Hz

(4) 286.5 Hz

(1) $n\text{'}=n \left(\frac{v}{v+{v}_{S}}\right)=800 \left(\frac{330}{330+30}\right) =733.33 Hz$.

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