When applying a linearly polarized beam to a half wave-plate, it emerges as a linearly polarized beam but its polarization plane is rotated with respect to the polarization plane of the input beam. The rotation of the polarization plane is such that the angle between the input polarization and the output polarization is twice the angle between the input polarization and the wave-plate's axis. When applying a circularly polarized beam, a clockwise circular polarization will transform into a counter-clockwise circular polarization and vice versa. Half wave-plates are often used as continuously adjustable polarization rotators and as a variable ratio beam splitter when used in conjunction with a polarization beam splitter cube.