Question

A tuning fork vibrates with frequency $256Hz$ and gives one best per second with the third normal mode of vibration of an open pipe. What is the length of the pipe? (Speed of sound of air is $340m{s}^{-1}$)

• A. $190cm$
• B. $180cm$
• C. $220cm$
• D. $200cm$

Answer 1

Answer: (D)

$200cm$

Frequency of tuning fork = $256$ Hz

Frequency of open pipe = $256\pm 1$ Hz

Frequency of third normal mode of vibration of an open pipe is $\nu =\frac{3v}{2l}$

here l = length of pipe

$\frac{3\times 340}{2\times l}=255$

$l=200cm$