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A train, standing in a station yard, blows a whistle of frequency 400 Hz in still air. The wind starts blowing in the direction from the yard to the station with a speed of 10 m/s. Given that the speed of sound in still air is 340 m/s
A train, standing in a station yard, blows a whistle of frequency 400 Hz in still air. The wind starts blowing in the direction from the yard to the station with a speed of 10 m/s. Given that the speed of sound in still air is 340 m/s
CBSE | Class 11 | NCERT Exemplar | Physics | Waves
A train, standing in a station yard, blows a whistle of frequency 400 Hz in still air. The wind starts blowing in the direction from the yard to the station with a speed of 10 m/s. Given that the speed of sound in still air is 340 m/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 observer standing on the platform is 350 m/s

c) the frequency of sound as heard by the observer standing on the platform will increase

d) the frequency of sound as heard by the observer standing on the platform will decrease

Answer:

The correct options are

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

b) the speed of sound for the observer standing on the platform is 350 m/s

Explanation:


The frequency of sound remains fixed since there is no relative motion between the source and the observer. As a result, the sound frequency detected by an observer standing on the platform is 400Hz.
Because the wind is blowing in the direction of the sound, the speed of the sound is as follows for a platform observer.
Speed of the sound 

i

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