Economical Device for Wavelength Measurement.
Measure the frequency and wavelength of the tone generated by a tuning fork or audio oscillator driven speaker with this simple device. It consists of a 91cm long acrylic tube with a diameter of 1.2cm, a sliding piston mounted on a wood dowel to vary the length of the air column in the tube, two steel supports and instructions.
Caution: WARNING: CHOKING HAZARD–Small parts. Not for children under 3 yrs.