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A train, standing in a station yard, blo...

A train, standing in a station yard, blows a whistle of frequency 400Hz in still air. The wind starts blowing in the direction from the yard to the station with a speed of 10m//s. Given that the speed sound in still air is `34om//s,

A

the frequency of sound as heard by an observer standing on the platform is 400 Hz

B

the speed of sound for the observed standing on the platform is 350 m/s

C

the frequency of sound as heard by the oberver standing on the platform will increases

D

the fequency of sound as heard by the observer standing on the platform will decreases

Text Solution

Verified by Experts

The correct Answer is:
A, B
Given , `" " v_(0)=400Hz, v=340 m//s`
Speed of wind `" " v_(w)=10m//s`
(a) As both source and observer are stationary , hence frequency observed will be same as natural frequency `v_(0)=400Hz `
(b) The speed of sound `v=v+v_(w)`
`" =340 +10 =m//s`
(c) and (b) There will be no effect on frequency, because there is no relative motion between source and obserer hence (c), (d) are incorrect.
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