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 \(\frac{\lambda}{4}\)
(બંને ઉદગમની આવૃતિ $F_1= F_2=500\, Hz$ અને હવામાં ધ્વનિનો વેગ $=330\, m / s$ છે.)