Resonance physics

An experiment is performed to determine the pitch of a tuning fork in air. The tuning fork is struck and held above a glass tube. The glass tube contains water, which is slowly drained. At various column lengths, the tube resonates and emits a frequency identical to that of the tuning fork. This resonance effect repeats itself every one-half wavelength. 11. If the speed of sound is 331 m/s and the spacing between the resonance points is 80.0 cm, determine the tuning fork's frequency. [207 Hz]