Dear Student,

First Part:

• The air at the closed end is not free to vibrate so a node is fromed at the closed end.
• While the air at the open end is free to vibrate with maximum amplitude so an antinodes is formed at this end.
• This is the simplest mode of vibration and it is called fundamental mode.

Second Part:

This frequency is called the fifth harmonic or second overtone. Thus we see that frequencies of the modes of vibrations are in the ratio n:n1:n2: = 1:3:5 This shows that only odd harmonics are present in the modes of vibrations of the air column closed at one end.

Thank You.