High Quality Content by WIKIPEDIA articles! The wave propagation speed in meter per second is the speed at which a wavefront (e.g. an acoustic signal or en electro-magnetic signal such as a radio wavefront, a light pulse in a fibre channel or a change of the electrical voltage on a copper wire) passes through a medium. The propagation speed for transmission in a vacuum, for example wireless communication, is the speed of light, meaning that the VoP of 1 (100%). In electrical cables, the speed mainly depends on the isolating material (see table below). The velocity of propagation (VoP) or velocity factor (VF) is a parameter expressed as a number between 0 and 1, or a percentage, that reflects the ratio of a signal's transmission speed to the speed of light in vacuum. In vacuum, VoP is 1. See also refractive index.