A long glass tube is held vertically , dipping into water, while a tuning fork of frequency `512 H_(Z)` is respeatedly struck and held over the open end. Strong resonance is obtained, when the length of the tube above the surface of water is `50 cm` and again `84 cm`, but not at any intermediate point. Find the speed of sound of sound in air and next length of the air column for resonance.
