Question

stationary wave in open organ pipe

Answer 1

The harmonics of frequencies 2n1, 4n1, 6n1, …, are missing. Hence, musical sound produced by an open organ pipe is sweeter than that produced by a closed organ pipe. Harmonics are the notes/sounds of frequency equal to or an integral multiple of fundamental frequency (n).
hope it helps you

Answer 2

this is due to the guage pressure vanishes at the end of the tube and too due to the boundary condition imposed at the end