### Telecommunications Definitions 6,209 > W 116

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### Wafer

• A thin slice of semiconducting material, such as a silicon crystal, upon which microcircuits are constructed by diffusion and deposition of various materials. Note: Millions of individual circuit elements, constituting hundreds of microcircuits, may be constructed on a single wafer. The individual microcircuits are separated by scoring and breaking the wafer into individual chips ("dice").

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### wave impedance

• At a point in an electromagnetic wave, the ratio of the electric field strength to the magnetic field strength. Note 1: If the electric field strength is expressed in volts per meter and the magnetic field strength is expressed in ampere-turns per meter, the wave impedance will have the units of ohms. The wave impedance, Z, of an electromagnetic wave is given by where is the magnetic permeability and ε is the electric permittivity. For free space, these values are 4 ÃÂ 10-7 H/m (henries per meter) and (1/36 ) F/m (farads per meter), from which 120 , i.e., 377, ohms is obtained. In dielectric materials, the wave impedance is 377/n, where n is the refractive index. Note 2: Although the ratio is called the wave impedance, it is also the impedance of the free space or the material medium.

• Browse Related Terms: characteristic impedance (Zo), field intensity, field strength, Maxwell's equations, mode, primary time standard, root-mean-square (rms) deviation, shield, wave equation, wave impedance

### waveguide

• A material medium that confines and guides a propagating electromagnetic wave. Note 1: In the microwave regime, a waveguide normally consists of a hollow metallic conductor, usually rectangular, elliptical, or circular in cross section. This type of waveguide may, under certain conditions, contain a solid or gaseous dielectric material. Note 2: In the optical regime, a waveguide used as a long transmission line consists of a solid dielectric filament (optical fiber), usually circular in cross section. In integrated optical circuits an optical waveguide may consist of a thin dielectric film. Note 3: In the rf regime, ionized layers of the stratosphere and refractive surfaces of the troposphere may also act as a waveguide.

• Browse Related Terms: cladding diameter, concentricity error, core diameter, ovality, self-focusing, tolerance field, waveguide

### waveguide scattering

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