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skin depth

1. n. [Geophysics]

The effective depth of penetration of an electromagnetic wave in a conductive medium. The skin depth is the distance in which the wave decays to 1/e (about 37%) of its value; it can be expressed as:

δs = (2/σμω)1/2 = (2/σ)(ε/μ)1/2,

δs = skin depth
σ = electrical conductivity
ω = 2πf = angular frequency in radians/s
f = frequency in Hz
μ = μrμ0 = magnetic permeability
μr = relative magnetic permeability of the conductor
μ0 = relative magnetic permeability of free space = 4π × 10−7 newton per ampere squared (N/A2)
ε = εrε0 = dielectric permittivity
εr = relative dielectric permittivity of the material
ε0 = dielectric permittivity of free space = 8.854 × 10−12 farads per meter (F/m).

See: electromagnetic methodpermeability