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

Gujarat BoardEnglish MediumSTD 11 SciencePhysics14. waves and sound1 Mark
MCQ
Two tuning forks, $A$ and $B$, give $4$ beats per second when sounded together. The frequency of $A$ is $320 Hz.$ When some wax is added to $B$ and it is sounded with $A, 4$ beats per second are again heard. The frequency of $B$ is  .... $Hz$
  • A
    $312$
  • B
    $316 $
  • ✓
    $324$
  • D
    $328$
✓

Answer

Correct option: C.
$324$
c
(c) $n_A -n_B \downarrow  = x$ (same) ... $(i)$ $\rightarrow$ Wrong
$n_B \downarrow  -n_A = x$ (same) ... $(ii)$ $\rightarrow$ Correct
==> $n_B = n_A + x = 320 + 4 = 324 Hz.$

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