In physics, a wavefront is the locus of points characterized by propagation of position of the same phase: a propagation of a line in 1d, a curve in 2d or a surface for a wave in 3d. Since infrared, optical, x-ray and gamma-ray frequencies are so high, the temporal component of electromagnetic waves is usually ignored at these wavelengths, and it is only the phase of the spatial oscillation that is described. Additionally, most optical systems and detectors are indifferent to polarization, so this property of the wave is also usually ignored. At radio wavelengths, the polarization becomes more important, and receivers are usually phase-sensitive. Many audio detectors are also phase-sensitive.