question_answer

In 1 m long open pipe what is the harmonic of resonance obtained with a tuning fork of frequency 480 Hz?

A)  First                                     

B)  Second

C)  Third                                    

D)  Fourth

Correct Answer: C

Solution :

                 For an open pipe of length\[l,\]the frequency n is given by \[n=n.\frac{v}{2l}\]        where v is velocity of sound,\[n\] the overtone.                 Given,   \[n=480\text{ }Hz,\text{ }l=1\text{ }m;\] \[v=330\text{ }m/s\]                 \[n=\frac{n(2l)}{v}\]                 \[=\frac{480\times 2\times 1}{330}=2.9\approx 3\] Hence, this is the second overtone or third harmonic.