In a closed pipe \(f=\frac{(2 P+1)}{4 I} v\)
For third overtone \((f)=\frac{7 v}{4 l}\)
\(\lambda=\frac{v}{f}=\frac{v}{7 v} \times 4 l\)
\(\lambda=\frac{4 l}{7}\)
\(\lambda=\frac{4 \times 105}{7}\)
\(\lambda=60 \,cm\)
First pressure node will be formed \(\frac{\lambda}{4}\)
${y}=1.0\, {mm} \cos \left(1.57 \,{cm}^{-1}\right) {x} \sin \left(78.5\, {s}^{-1}\right) {t}$
${x}>0$ ના ક્ષેત્રમાં ઉગમબિંદુથી નજીકનું નિસ્પંદ બિંદુ ${x}=\ldots \ldots \ldots\, {cm}$ અંતરે હશે.