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14. waves and sound — Physics STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 SciencePhysics14. waves and sound1 Mark
MCQ
A police car horn emits a sound at a frequency $240 Hz$ when the car is at rest. If the speed of the sound is $330 m/s$, the frequency heard by an observer who is approaching the car at a speed of $11 m/s,$ is ... $Hz$
  • ✓
    $248$
  • B
    $244 $
  • C
    $240 $
  • D
    $230 $
✓

Answer

Correct option: A.
$248$
a
(a) Frequency heard by the observer
$n' = n\,\left( {\frac{{v + {v_0}}}{v}} \right) = 240\,\left( {\frac{{330 + 11}}{{330}}} \right) = 248Hz.$

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