1. The problem statement, all variables and given/known data One end of a plastic tube, open at both ends, is placed into a large container of water. A 256 Hz tuning fork, continuously vibrating, is held over the end of the tube in the air and the tube is raised until maximum loudness is observed. The plastic tube is then raised until the next position of maximum loudness is found. This new position is 65 cm higher than the first. Calculate the speed of sound. 2. Relevant equations v = f x λ λ = 4 x L (L = length of tube) 3. The attempt at a solution Since this is a closed ended column of air, only the odd harmonics are capable of resonating. Thus the two positions must correspond to a frequency difference of 512 HZ (ie. the difference between successive odd harmonics). The 65 cm difference in tube length must correspond to the wavelength. The first situation λ1 = 4 x L. In the second situation, λ2 = 4(L+.65) Anyway, here is where I keep getting bogged down. The velocity has to be the same in both situations, so v = f1λ1 = f2λ2 or f1(4L) = f2 (4L + 2.60) Also f1 - f2 = 512 3 variables and 2 equations...seems like I am over-complicating this problem, but if I can figure out either of the sets of frequency and wavelength in the two situations I should be good to go. What am I missing?