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

Gujarat BoardEnglish MediumSTD 11 SciencePhysics14. waves and sound1 Mark
MCQ
A source of sound of frequency $n$ is moving towards a stationary observer with a speed $S.$ If the speed of sound in air is $V$ and the frequency heard by the observer is ${n_1}$, the value of ${n_1}/n$ is
  • A
    $(V + S)/V$
  • B
    $V/(V + S)$
  • C
    $(V - S)/V$
  • ✓
    $V/(V - S)$
✓

Answer

Correct option: D.
$V/(V - S)$
d
(d) By using $n' = n\frac{v}{{v - {v_S}}}$

==> $\frac{{{n_1}}}{n} = \left( {\frac{V}{{V - S}}} \right)$

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