An organ pipe of length 3.0 m has one end closed. The longest and next-longest possible wavelengths for standing waves inside the pipe are
A) 6 m and 3 m.
B) 12 m and 6 m.
C) 12 m and 4 m.
D) 9 m and 6 m.
E) 3 m and 1.5 m.

Question

Quizplus · Accepted Answer

For a pipe with one end closed, the allowed wavelengths are given by:
λn = 4L/n where n is an odd integer.
The longest wavelength will be for n=1: 
λ1 = 4L/1 = 12 m
The next longest wavelength will be for n=3:
λ3 = 4L/3 = 4 m
Therefore, the longest and next-longest possible wavelengths for standing waves inside the pipe are 12 m and 4 m respectively. The correct choice is C.

An Organ Pipe of Length 3