Shows how the addition of two plane polarised waves with an arbitrary phase difference can combine to produce other polarisations, including circularly or elliptically polarised light. Type in the input boxes to change the amplitudes, frequencies and phase difference of the waves; animate by clicking the play button or by using the time slider; right click on the tip of the resultant E-field vector and turn on the trace to show the pattern traced by the resultant E-field amplitude.