Wave impedance: At a point in an electromagnetic wave, the ratio of the electric field strength to the magnetic field strength. Electromagnetic radiation is a propagating wave in space with electric and magnetic components. ... In number and more generally in algebra, a ratio is the linear relationship between two quantities of the same unit. ... In physics, an electric field or E-field is an effect produced by an electric charge (or a time-varying magnetic field) that exerts a force on charged objects in the field. ... It has been suggested that Magnetic field density be merged into this article or section. ...

Note 1: If the electric field strength is expressed in volts per metre (V/m) and the magnetic field strength is expressed in ampere-turns per metre (A·t / m), the wave impedance will have the units of ohms. The wave impedance, Z , of an electromagnetic wave is given by the equation: ʐIn physics, the field strength of a field is the magnitude of its vector (spatial) value. ... The volt (symbol: V) is the SI derived unit of electric potential difference. ... The metre (Commonwealth English) or meter (American English) (symbol: m) is the SI base unit of length. ... The ampere (symbol: A) is the SI base unit of electric current equal to one coulomb per second. ... The concept wave is related to a disturbance that propagates through space, often transferring energy. ... In electrical engineering, Impedance is a measure of opposition to a sinusoidal electric current. ... Ohm may refer to: The scientist Georg Ohm. ... In mathematics, one often (not quite always) distinguishes between an identity, which is an assertion that two expressions are equal regardless of the values of any variables that occur within them, and an equation, which may be true for only some (or none) of the values of any such variables. ...

Where μ is the magnetic permeability, ε is the electric permittivity and σ is the conductivity of the material the wave is travelling through. In the equation, i is the imaginary unit, and ω is the angular frequency of the wave. In the case of a dielectric (where conductivity is zero), the equation reduces to: This article is in need of attention. ... Permittivity is a physical quantity that describes how an electric field affects and is affected by a medium. ... Electrical conductivity is a measure of how well a material accommodates the transport of electric charge. ... In mathematics, the imaginary unit i (sometimes also represented by the Latin j or the Greek iota, but in this article i will be used exclusively) allows the real number system to be extended to the complex number system . ... Angular frequency is a measure of how fast an object is rotating In physics (specifically mechanics and electrical engineering), angular frequency ω (also called angular speed) is a scalar measure of rotation rate. ... A dielectric, or electrical insulator, is a substance that is highly resistant to the flow of electric current and has a relative permittivity greater than unity. ...

For free space, μ is 4π × 10^-7 H/m (henries per metre) and ε is 8.854 × 10^-12 F/m (farads per metre), from which Z ≈ 377 ohms is obtained. In physics, free space is a concept of electromagnetic theory, corresponding roughly to the vacuum, the baseline state of the electromagnetic field, or the replacement for the electromagnetic aether. ... The henry (symbol: H) is the SI unit of inductance. ... The farad (symbol: F) is the SI unit of capacitance. ...

In a perfect dielectric (where conductivity is zero), the wave impedance is 377/n, where n is the refractive index. In a lossy dielectric or a conductor (where conductivity is greater than zero), the wave impedance will be a complex number. A dielectric, or electrical insulator, is a substance that is highly resistant to the flow of electric current and has a relative permittivity greater than unity. ... In electrical engineering, Impedance is a measure of opposition to a sinusoidal electric current. ... The refractive index of a material is the factor by which the phase velocity of electromagnetic radiation is slowed relative to vacuum. ... In science and engineering, conductors are materials that contain movable charges of electricity. ... Wikibooks Algebra has more about this subject: Complex numbers In mathematics, a complex number is an expression of the form where a and b are real numbers, and i represents the imaginary unit, i2 = −1. ...

Note 2: Although the ratio is called the wave impedance, it is also the impedance of the free space or the material (medium). In physics, free space is a concept of electromagnetic theory, corresponding roughly to the vacuum, the baseline state of the electromagnetic field, or the replacement for the electromagnetic aether. ... For other meanings of medium, see Medium (disambiguation). ...

Note 3: The symbol η (eta) is often used instead of Z for wave impedance to avoid confusion with electrical impedance. The neutrality of this introduction is disputed. ... Electrical impedance or simply impedance is a measure of opposition to a sinusoidal electric current. ...

Source: from Federal Standard 1037C and from MIL-STD-188 Federal Standard 1037C entitled Telecommunications: Glossary of Telecommunication Terms is a U.S. Federal Standard, issued by the General Services Administration pursuant to the Federal Property and Administrative Services Act of 1949, as amended. ... MIL-STD-188 is a series of U.S. military standards relating to telecommunications. ...