J & K CET Engineering
J and K - CET Engineering Solved Paper-2005
question_answer
In \[1\text{ }m\]long open pipe what is the harmonic of resonance obtained with a tuning fork of frequency \[480\text{ }Hz\]?
A) First
B) Second
C) Third
D) Fourth
Correct Answer:
C
Solution :
For an open pipe of length the frequency n is given by \[n=n'\frac{v}{2l}\] where v is velocity of sound, n' the overtone. Given, \[n=480\,Hz,\,\,l=1m,\] \[v=330\text{ }m/s\] \[n'=\frac{n(2)}{v}\] \[=\frac{480\times 2\times 1}{330}=2.9\approx 3\] Hence, this is the second overtone or third harmonic.