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A whistle emitting a sound of frequency ...


A whistle emitting a sound of frequency `440 H`z is tied to string of `1.5 m` length and rotated with an angular velocity of `20 rad//sec` in the horizontal plane. Then the range of frequencies heard by an observer stationed at a large distance from the whistle will `(v=330 m//s)`

A

`400.0 Hz` to `484.0 Hz`

B

`403.3 Hz` to `480.0 Hz`

C

`400.0 Hz` to `480.0 Hz`

D

`403.3` Hz to `484.0 Hz`

Text Solution

Verified by Experts

The correct Answer is:
D

Frequency heard by the observed will be maximum when the source is in the position D. Inthis case source will be approaching towards the stationary observer, almost along the line of sight (as observer is stationed at a larger distance.)
Similarly frequency heard by the observer will be minimum when the source reaches at the position B. Now the source will be moving away from the observer.
`n_(min)=(v)/(v+v_S)xxn=(330)/(330+1.5xx20)xx440`
`=(330xx440)/(360)=403.3Hz`
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