A source and an observer are situated on two perpendicular tracks as shown in the figure. The observer is at rest and the source is moving with a speed of 50 m s - 1 . The source emits a sound wave of

Question

A source and an observer are situated on two perpendicular tracks as shown in the figure. The observer is at rest and the source is moving with a speed of $50 m s^{- 1}$ . The source emits a sound wave of frequency $75 Hz$ , which travel in the medium with a velocity of $200 m s^{- 1}$ . The frequency of the sound heard by the observer when the source crosses the origin is

TestHub · Accepted Answer

At the time of emission, if the source and observer line is making an angle $θ$ with the line of motion of source, then

$f_{app} = f_{o} (\frac{v}{v - v_{s} cosθ})$

$x = v_{s} t$ and $x = lcosθ$

[As this sound is heard by observer when source is at $O$ ]

$∴ cosθ = (\frac{v_{s}}{v})$
and $f_{app} = f_{o} (\frac{v^{2}}{v^{2} - v_{s}^{2}})$
Putting the values, $f_{app} = 80 Hz$

Physics - Sound Wave Question with Solution | TestHub

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