Question

The two nearest harmonics of a tube closed at one end and open at other end are $220Hz$ and $260Hz$ . What is the fundamental frequency of the system ?

• A. 20 Hz
• B. 30 Hz
• C. 40 Hz
• D. 10 Hz

Answer 1

Answer: (A)

Sol. Two successive frequencies of closed pipe
$\frac{nv}{4l}=220$...(i)
$\frac{(n+2)v}{4l}=260$...(ii)
Dividing (ii) by (i), we get
$\frac{n+2}{n}=\frac{260}{220}=\frac{13}{11}$
$11n+22=13n$
$n=11$
So, $11\frac{v}{4I}=220$
$\frac{v}{4l}=20$
So fundamental frequency is $20Hz$.