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The choice of sign for time-dependence, e −iωt, dictates the sign convention for the imaginary part of permittivity. The signs used here correspond to those commonly used in physics, whereas for the engineering convention one should reverse all imaginary quantities.
The relative permittivity (in older texts, dielectric constant) is the permittivity of a material expressed as a ratio with the electric permittivity of a vacuum. A dielectric is an insulating material, and the dielectric constant of an insulator measures the ability of the insulator to store electric energy in an electrical field.
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 represented by the symbol Y 0 .
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.
The sign for the imaginary part of permittivity (in fact dictated by the choice of sign for time-dependence). The signs of distances and radii of curvature of optical surfaces in optics. The sign of work in the first law of thermodynamics. The sign of the weight of a tensor density, such as the weight of the determinant of the covariant metric ...
In attenuating media, the same relation is used, but the permittivity is allowed to be a complex number, called complex electric permittivity: [3] _ = _, _ = _, where ε is the complex electric permittivity of the medium.
permittivity: farad per meter (F/m) strain: unitless epsilon nought Vacuum permittivity: farad per meter (F/m) zeta: damping ratio: unitless eta: angular jerk: radian per second cubed (rad⋅s −3) energy efficiency: unitless (dynamic) viscosity (also )
The real (blue solid line) and imaginary (orange dashed line) components of relative permittivity are plotted for model with parameters = 3.2 eV, = 4.5 eV, = 100 eV, = 1 eV, and = 3.5. The Tauc–Lorentz model is a mathematical formula for the frequency dependence of the complex-valued relative permittivity , sometimes referred to as the ...