You can select the form of the tube by using the appropriate radio buttons ("both sides open", "one side open" and "both dides closed"). It is possible to switch to the next harmonic by pressing the button "Lower" respectively "Higher". The applet shows the harmonics up to the fifth upper oscillation.
If you write a new value for the length of the tube into the textfield and press the "Enter" key, the applet will calculate wavelength and frequency. The speed of sound was presupposed as 343.5 m/s, corresponding to a temperature of 20 °C. The influence of the tube's diameter is neglected.