mudit......this is a prob. similar to the fiitjee one yaar......(hope it clicked)....dekho looking at the 660 ms....for the speed of sound...it is not a negligable distance.....(sound takes 2 secs to travel this distance)...toh...

firstly...if a perticular wave of sound reaches the observer when the emmiter passes the origine....then it shud have been emmitted a while ago be the emmiter....

say when it was at a pt (0, -y)......then say y= vt............v= velocity of sound emmiter

but evn root( y²+(660)²) = Vt.......(V= velocity of sound)

toh using this we have y

using y we have cos @.....(@ the angle btween the line joining (o,-y) and (660,0) and y axis)

and we apply the dopplers formula at this instant....

pardon ne silly mistakes but i guess the method is sumwhat the same.......

the main logic is that we analyse the wave not emmited at the instant when it is at the origine but that one which is emmitted by it when it is at some instant before it comes to the origine where that distance is such that by the time the emmiter covers this distace to come to the origine the wave reaches the observer.......

hope it makes sense.....

rate if useful........