Waves Ques 1
1. A tuning fork with frequency $800$ $ \mathrm{Hz}$ produces resonance in a resonance column tube with upper end open and lower end closed by water surface. Successive resonance are observed at lengths $9.75 $ $\mathrm{cm}, 31.25$ $ \mathrm{cm}$ and $52.75 $ $\mathrm{cm}$. The speed of sound in air is,
[NEET Odisha 2019]
(a) $172$ $ \mathrm{m} / \mathrm{s}$
(b) $500 $ $\mathrm{m} / \mathrm{s}$
(c) $156$ $ \mathrm{m} / \mathrm{s}$
(d) $344 $ $\mathrm{m} / \mathrm{s}$
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Answer:
Correct Answer: 1.(d)
Solution: (d) $l_1 =9.75 $ $\mathrm{cm} $
$l_2 =31.25 $ $\mathrm{cm} $
$l_3 =52.75 $ $\mathrm{cm} $
$e =\text { end correction } $
$\frac{\lambda}{4} +e=9.75 $ $\mathrm{cm} $
$\frac{3 \lambda}{4} +e=31.25 $ $\mathrm{cm} $
$\frac{3 \lambda}{4} -\frac{\lambda}{4}=31.25-9.75 $
$\frac{\lambda}{2} =21.5 $
$\lambda =43 $ $\mathrm{cm} $
$v =\lambda \times f $
$v =34400 \times 10^{-2} $
$\therefore \quad v =344 $ $\mathrm{ms}^{-1}$
BETA
