Standing waves differ from propagating waves by the fact that the particles are in the same or in the opposite phase of oscillation at all times. A standing wave can be explained by superposition of the incidenting wave and the reflected wave. Two cases are to be distinguished:
This HTML5 app illustrates the incidenting wave (red), the reflected wave (blue), and the standing wave resulting from superposition (black). The control panel provides the choice between reflection from a fixed end and reflection from a free end. The "Reset" button brings the simulation into the initial state. The other button is for starting, pausing or continuing the simulation. If you choose the option "Slow motion", the animation will run 10× slower. There is also a selection between a continuous animation and a single-step illustration, whereby the time interval can be set. In the option fields at the very bottom, one can determine which waves should be visible.