Hello. I'm having some trouble with this problem: A tuning fork is set into vibration above a vertical open tube filled w/ water. Water level is dropping slowly. As it does so, the air in the tube above the water level is heard to resonate w/ the tuning fork when the distance from the tube opening to the water level is 0.125 m and again at 0.395m. What is the frequency of the tuning fork? So I subtracted the two distances and got (n+2)L - nL = .395 - .125 = .270 m Are 0.125m and 0.395 successive though ? Now I'm stuck. Any help would be appreciated.