A pipe 30 cm long is open at both ends. The speed of sound in air is  330ms^-1 . Which harmonic mode of the pipe resonates at 1.1 kHz source?

In an open organ pipe, the frequency of its nth harmonic is
${\mathrm{v}}_{\mathrm{n}}=\frac{\mathrm{nv}}{2\mathrm{L}},\text{ where }\mathrm{n}=1,2,3,\dots \dots$(1)
Given, l =30 cm=0.3 m and v = 330 $m{s}^{-1}.$

Substituting the given values in Eq. (i), we get
$1.1\times {10}^3=\frac{\mathrm{n}\times 330}{2\times 0.3}=\left(\frac{\mathrm{n}\times 330}{0.6}\right)$
n = 2