Standing Sound Waves?

Question

You are studying standing sound waves in an organ pipe of length L with both ends open. What wavelengths of sound can exist as standing waves in this pipe? Express your answer in terms of the length L.

For this I had lambda = (3L) / 2. The question also asks for an organ pipe of length L with one end open and one end closed but I don't know (maybe 5L / 2??).

Answer 1

Wavelengths resonated by pipes of length L:
Both ends open: integer divisors of 2 * the pipe length (2L/1, 2L/2, etc);
One end open: odd-integer divisors of 4 * the pipe length 4L/1, 4L/3, etc.).
It's the frequencies that multiply by integers or odd integers.
See the refs.