Question

A resonance tube of length 1 m is resonated with a tuning fork of frequency 300 Hz. If the velocity of sound in air is $300m{s}^{-1}$ then the number of harmonics produced in the tube will be

• A. 1
• B. 2
• C. 3
• D. 4

Answer 1

Answer: (B)

2

From the formula , $v=f\lambda$ , we get ,

$\lambda =v/f=300/300=1m$ ,

let the lengths of resonant columns be $l_1,l^{}$ and $l_3$ , therefore

for first resonance ,

$l_1=\lambda /4=1/4=0.25m$ ,

for second resonance ,

$l_2=3\lambda /4=1/4=0.75m$ ,

for third resonance ,

$l_3=5\lambda /4=1/4=1.25m$ ,

it is clear that only two harmonics are possible , because $l_3$ is greater than total length $1m$ of tube .