In this mode of vibration, there is one node at the centre of the pipe and two antinodes, one at each open end as shown in figure (a).
Equation (3) represents fundamental frequency or lowest frequency of vibration
ii. Second mode or first overtone:
In this mode of vibration, there are two nodes and three antinodes as shown in figure (b).
Thus, frequency of first overtone (second harmonic) is twice the fundamental frequency
iii. Third mode or second overtone:
In this mode of vibration, there are 3 nodes and 4 antinodes as shown in figure (C).
Let,
v = wave velocity in air (As the medium is same, wave velocity remains same)
n2 = next higher frequency
Thus, frequency of second overtone is thrice the fundamental frequency.
