The velocity factor (VF), also called wave propagation speed or velocity of propagation (VoP or ), of a transmission medium is the speed at which a wavefront (of an acoustic signal, for example, or an electromagnetic signal, a radio signal, a light pulse in a fibre channel or a change of the electrical voltage on a copper wire) passes through the medium, relative to the speed of light. For optical signals, the velocity factor is the reciprocal of the refractive index.
The speed of radio signals in a vacuum, for example, is the speed of light, and so the velocity factor of a radio wave in a vacuum is unity, or 100%. In electrical cables, the velocity factor mainly depends on the insulating material (see table below).
The use of the terms velocity of propagation and wave propagation speed to mean a ratio of speeds is confined to the computer networking and cable industries. In a general science and engineering context, these terms would be understood to mean a true speed or velocity in units of distance per time, while velocity factor is used for the ratio.
Read more about Wave Propagation Speed: Typical Velocity Factors, Calculating Velocity Factor
Famous quotes containing the words wave and/or speed:
“Through this broad street, restless ever,
Ebbs and flows a human tide,
Wave on wave a living river;
Wealth and fashion side by side;
Toiler, idler, slave and master, in the same quick current glide.”
—John Greenleaf Whittier (1807–1892)
“For myself and my loved ones, I want the heat, which comes at the speed of light. I don’t want to have to hang about for the blast, which idles along at the speed of sound.”
—Martin Amis (b. 1949)