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

Gujarat BoardEnglish MediumSTD 11 SciencePhysics14. waves and sound1 Mark
MCQ
Two perfectly identical wires are in unison. When the tension in one wire is increased by $1\%$, then on sounding them together $3$ beats are heard in $2 \,sec$. The initial frequency of each wire is .... ${\sec ^{ - 1}}$
  • A
    $220$
  • B
    $320$
  • C
    $150$
  • ✓
    $300$
✓

Answer

Correct option: D.
$300$
d
(d) Initial frequency of each wire $(n)$

$ = \frac{{{\rm{(Number}}\;{\rm{of}}\;{\rm{beats}}\;{\rm{heared}}\;{\rm{per}}\;{\rm{sec)}} \times {\rm{200}}}}{{{\rm{(per}}\;{\rm{centage}}\;{\rm{change}}\;{\rm{in}}\;{\rm{tension}}\;{\rm{of}}\;{\rm{the}}\;{\rm{wire)}}}}$

$ = \frac{{(3/2) \times 200}}{1} = 300{\sec ^{ - 1}}$

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