The polarization of an electromagnetic wave describes the orientation of the oscillating electric field. The wave is transverse and travels in the positive direction. There is also a magnetic field in phase with the electric field and perpendicular to both the electric field and the direction of propagation. The electric field may be divided into two perpendicular components labeled and , such that , where is the phase difference between the two components. When or , the wave is said to be linearly polarized. If and has the same magnitude as , then the wave is said to be circularly polarized; in all other cases, the wave is elliptically polarized.