JEE Advanced2013PhysicsWaves and SoundActual
Two vehicles, each moving with speed u on the same horizontal straight road, are approaching each other. Wind blows along the road with velocity w. One of these vehicles blows a whistle of frequency f 1 . An observer in the other vehicle hears the frequency of the whistle to be f 2 . The speed of sound in still air is V. The correct statement (s) is (are) :
Options
- AIf the wind blows from the observer to the source, f 2 > f 1 .
- BIf the wind blows from the source to the observer, f 2 > f 1 .
- CIf the wind blows from the observer to the source, f 2 < f 1 .
- DIf the wind blows from the source to the observer, f 2 < f 1 .
Correct answer
A. If the wind blows from the observer to the source, f 2 > f 1 .
Step-by-step solution
If wind blows from source to observer f 2 = v + w + u v + w - u f 1 ⇒ f 2 > f 1 If wind blows from observer to source f 2 = v - w + u v - w - u f 1 ⇒ f 2 > f 1