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

Gujarat BoardEnglish MediumSTD 11 SciencePhysics14. waves and sound1 Mark
MCQ
A set of $20$ tuning forks is arranged in a series of increasing frequencies. If each fork gives $4$ beats with respect to the preceding fork and the frequency of the last fork is twice the frequency of the first, then the frequency of last fork is $\dots \; Hz$.
  • A
    $151$
  • ✓
    $152$
  • C
    $153$
  • D
    $154$
✓

Answer

Correct option: B.
$152$
b
$f_{1}= f$

$f _{2}= f +4$

$f _{3}= f +2 \times 4$

$f _{4}= f +3 \times 4$

$f _{20}= f +19 \times 4$

$f +(19 \times 4)=2 \times f$

$f =76 \; Hz$

Frequency of last tuning forks $=2 \; f$

$=152 \; Hz$

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