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The velocity factor (VF), [1] also called wave propagation speed or velocity of propagation (VoP or ), [2] of a transmission medium is the ratio of the speed at which a wavefront (of an electromagnetic signal, a radio signal, a light pulse in an optical fibre or a change of the electrical voltage on a copper wire) passes through the medium, to the speed of light in vacuum.
The absolute refractive index n of an optical medium is defined as the ratio of the speed of light in vacuum, c = 299 792 458 m/s, and the phase velocity v of light in the medium, =. Since c is constant, n is inversely proportional to v : n ∝ 1 v . {\displaystyle n\propto {\frac {1}{v}}.}
Snell's law. Refraction of light at the interface between two media of different refractive indices, with n 2 > n 1. Since the velocity is lower in the second medium (v 2 < v 1), the angle of refraction θ 2 is less than the angle of incidence θ 1; that is, the ray in the higher-index medium is closer to the normal.
In the context of electromagnetics and optics, the frequency is some function ω(k) of the wave number, so in general, the phase velocity and the group velocity depend on specific medium and frequency. The ratio between the speed of light c and the phase velocity v p is known as the refractive index, n = c / v p = ck / ω.
Within optics, dispersion is a property of telecommunication signals along transmission lines (such as microwaves in coaxial cable) or the pulses of light in optical fiber. In optics, one important and familiar consequence of dispersion is the change in the angle of refraction of different colors of light, [2] as seen in the spectrum produced ...
An optical fiber, or optical fibre, is a flexible glass or plastic fiber that can transmit light [a] from one end to the other. Such fibers find wide usage in fiber-optic communications , where they permit transmission over longer distances and at higher bandwidths (data transfer rates) than electrical cables.
But, for optically transparent media, and for all other materials at optical frequencies (except possible metamaterials), μ rel is indeed very close to 1; that is, μ ≈ μ 0. In optics, one usually knows the refractive index n of the medium, which is the ratio of the speed of light in a vacuum (c) to the speed of
Fiber-optic communication is a method of transmitting information from one place to another by sending pulses of infrared or visible light through an optical fiber. [ 1 ] [ 2 ] The light is a form of carrier wave that is modulated to carry information. [ 3 ]