Interference simulates the interference between two circular waves, for instance waves in a ripple tank. You may vary the distance between the sources and the wavelength and watch the displacement pattern in 2D or 3D. The intensity pattern is also available. It is possible to generate, view and save animations of the interference pattern. The simulation images may be saved, printed or copied. Five integrated activities in html-format are included. These may be modified or a teacher may make his own activities.