The red arrow represents a vector made of two time dependant, harmonic, components [math]E_x[/math] (blue) and [math]E_y[/math] (green).[br][br] [math]\vec{E}=E_x.cos\left(\omega t\right)\vec{e_x}+E_y.cos\left(\omega t-\phi\right)\vec{e_y}[/math][br][br]According to the phase difference and the relative amplitudes of the components, the extremity of the red vector describes a :[br][br] - line : linear polarization [math]\phi=0[/math] or [math]\phi=\pi[/math][br] - an ellipse : elliptical polarization (arbitrary [math]\phi[/math])[br] - a circle : circular polarization ([math]E_x=E_y[/math] and [math]\phi=\frac{\pi}{2}[/math])[br]clock wise or anti-clock wise[br][br]click on the bottom left corner to start or stop the animation.[br]You can change the maximum amplitude of the components as well as the phase difference between the components[br][br]