If formula_13, the wave is linearly polarized. The ellipse collapses to a straight line formula_14) oriented at an angle formula_15. This is the case of superposition of two simple harmonic motions (in phase), one in the x direction with an amplitude formula_16, and the other in the y direction with an amplitude formula_17. When formula_18 increases from zero, i.e., assumes positive values, the line evolves into an ellipse that is being traced out in the counterclockwise direction (looking in the direction of the propagating wave); this then corresponds to "left-handed elliptical polarization"; the semi-major axis is now oriented at an angle formula_19. Similarly, if formula_18 becomes negative from zero, the line evolves into an ellipse that is being traced out in the clockwise direction; this corresponds to "right-handed elliptical polarization".