A train is approaching towards a platform with a speed of `10 ms^(-1)`, while blowing a whistle of frequency 340 Hz. What is the frequency of whistle heard by a stationary observer on the platform ?
(given, speed of sound `=340 ms^(-1)`)

Options

A. 330 Hz
B. 350 Hz
C. 340 Hz
D. 360 Hz

Answer

B

Explanation

Given, `v=340` Hz
[Frequency of sound produced by source]
Speed of sound `v=340 ms^(-1)`
Approaching speed of train, `v_(s)=10 ms^(-1), v'=`?
We know that when sound source is approaching a stationary and observer then frequency hard by the observer
`v'=v(v/(v-v_(s)))=340 (340/(340-10))=(340xx340)/330`
`=(340xx34)/33=11560/33=350.3~~350 Hz`