A siren emitting a sound of frequency 800 Hz
moves away from an observer towards a cliff at a
speed of 15 m/s. Then, the frequency of sound
that the observer hears in the echo reflected from
the cliff is :
(Take velocity of sound in air = 330 m/s)
(1) 765 Hz
(2) 800 Hz
(3) 838 Hz
(4) 885 Hz