Lossy Medium
Again, similar as for absolute permittivity, relative permittivity for lossy materials can be formulated as:
in terms of a "dielectric conductivity" σ (units S/m, siemens per meter), which "sums over all the dissipative effects of the material; it may represent an actual conductivity caused by migrating charge carriers and it may also refer to an energy loss associated with the dispersion of ε' " (, p. 8). Expanding the angular frequency ω = 2πc/λ and the electric constant ε0 = 1/(µ0c2), it reduces to:
where λ is the wavelength, c is the speed of light in vacuum and κ = µ0c/2π ≈ 60.0 S−1 is a newly-introduced constant (units reciprocal of siemens, such that σλκ = εr" remains unitless).
Read more about this topic: Relative Permittivity
Famous quotes containing the word medium:
“The essence of acting is the conveyance of truth through the medium of the actor’s mind and person. The science of acting deals with the perfecting of that medium.”
—Minnie Maddern Fiske (1865–1932)