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Vacuum permittivity, commonly denoted ε 0 (pronounced "epsilon nought" or "epsilon zero"), is the value of the absolute dielectric permittivity of classical vacuum. It may also be referred to as the permittivity of free space, the electric constant, or the distributed capacitance of the vacuum.
Another common term encountered for both absolute and relative permittivity is the dielectric constant which has been deprecated in physics and engineering [2] as well as in chemistry. [ 3 ] By definition, a perfect vacuum has a relative permittivity of exactly 1 whereas at standard temperature and pressure , air has a relative permittivity of ...
μ 0 ≈ 12.566 × 10 −7 H/m is the magnetic constant, also known as the permeability of free space, ε 0 ≈ 8.854 × 10 −12 F/m is the electric constant, also known as the permittivity of free space, c is the speed of light in free space, [9] [10] The reciprocal of Z 0 is sometimes referred to as the admittance of free space and ...
In the frequency region above ultraviolet, permittivity approaches the constant ε 0 in every substance, where ε 0 is the permittivity of the free space. Because permittivity indicates the strength of the relation between an electric field and polarisation, if a polarisation process loses its response, permittivity decreases.
ε 0 is the electric constant (a universal constant, also called the permittivity of free space) (ε 0 ≈ 8.854 187 817 × 10 −12 F/m) This relation is known as Gauss's law for electric fields in its integral form and it is one of Maxwell's equations.
The Fresnel equations ... where Z 0 is the impedance of free space and i = 1, 2. ... Hence we define the relative permittivity (or dielectric constant) ...
In free space the wave impedance of plane waves is: = (where ε 0 is the permittivity constant in free space and μ 0 is the permeability constant in free space). Now, since = = (by definition of the metre),
The electric displacement field "D" is defined as +, where is the vacuum permittivity (also called permittivity of free space), E is the electric field, and P is the (macroscopic) density of the permanent and induced electric dipole moments in the material, called the polarization density.