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

Gujarat BoardEnglish MediumSTD 11 SciencePhysics14. waves and sound1 Mark
MCQ
A Siren emitting sound of frequency $800 \;Hz$ is going away from a static listener with a speed of $30\; m/s$, frequency of the sound to be heard by the listener is... $Hz$ (take velocity of sound as $330 \;m/s$)
  • ✓
    $733.3$
  • B
    $644.8$
  • C
    $481.2$
  • D
    $286.5$
✓

Answer

Correct option: A.
$733.3$
a
(a) $n' = n\,\left( {\frac{v}{{v + {v_S}}}} \right) = 800\,\left( {\frac{{330}}{{330 + 30}}} \right)\, = 733.33\,Hz$.

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