1.

An observer moving with uniform velocity towards a stationary sound source observes frequency f = 170 hz over a distance of x = 80 m. If frequency of sound is f_(0) = 160 Hz and sound travel with speed c = 340 ms^(-1) , then duration of beep emitted by source is n. Find n.

Answer»


Solution :`f_(ab) = ((V+v_(ob))/(v))f_(0)`
`1 + (v_(ob))/(v) = (f_(ob))/(f_o)`
`v_(ob) = ((f_(ob)-f_(o))/(f_o))v`
`Delta tau = tau_(o) - tau_(ob) = L/(f_0) - L/(f_(ob))`
`Delta tau = (f_(ob)-f_(o))/(f_(o) CDOT f_(ob))`
Difference in time interval of BEEP observed and produced is no. of OSCILLATION multipled by `Delta tau`.
`t' = (Delta t)/(tau_(ob)) Delta tau`
`:. Delta t + t' = 4 "sec"`.


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