A train moves towards a stationary observer with speed `34 m//s`. The train sounds a whistle and its frequency registered by the observer is `f_(1)`. If the train's speed is reduced to `17 m//s`, the frequency registered is `f_(2)`. If the speed of sound of `340 m//s`, then the ratio `f_(1)//f_(2)`is

Options

A. `(18)/(19)`
B. `(1)/(2)`
C. `2`
D. `(19)/(18)`

Answer

D

Explanation

`f_(1)=f((v)/(v-v_(s)))rArr f_(1)=f((340)/(340-34))=f((340)/(306))`
and `f_(2)=f((340)/(340-17))=f((340)/(323)):. (f_(1))/(f_(2))=(323)/(306)=(19)/(18)`