Question

A tuning fork with frequency $800\, Hz$ produces resonance in a resonance column tube with upper end open and lower end closed by water surface. Successive resonance are observed at length $9.75\, cm$, $31.25\, cm$ and $52.75\, cm$. The speed of sound in air is :

• A. $500 \,m/s^{-1}$
• B. $156 \,m/s^{-1}$
• C. $344 \,m/s^{-1}$
• D. $172 \,m/s^{-1}$

Answer 1

Answer: (C)

$344 \,m/s^{-1}$

Answer 2

Here $\lambda = 2 (l_2 - l_1)$
where $l_1 = 9.75\,cm, l_2 = 31. 25\,cm$
so $v = 2n(l_2 - l_1) \times 800(31.25 - 9.75)$
$= 344 \,m/s$