A whistle producing sound waves of frequencies `9500 HZ` and above is approaching a stationary person with speed `vms^(-1)`. The velocity of sound in air is `300 ms^(-1)`. If the person can hear frequencies upto a maximum of `10,000 HZ`, the maximum value of `v` upto which he can hear whistle is

Options

A. (a) `15sqrt(2)`
B. (b) `15/sqrt(2)ms^(-1)`
C. ( c ) `15ms^(-1)``
D. (d) `30ms^(-1)`

Answer

C

Explanation

(c ) `v' = v[(v)/(v - v_(s))]` rArr `10000 = 9500[(300)/(300 - v)]`
rArr `300 - v = 300 xx 0.95` rArr `v = 300 - 285 =15 ms^(-1)`