Metals
Although permittivity is typically associated with dielectric materials, we may still speak of an effective permittivity of a metal, with real relative permittivity equal to one (, eq.(4.6), p. 121). In the low-frequency region (which extends from radiofrequencies to the far infrared region), the plasma frequency of the electron gas is much greater than the electromagnetic propagation frequency, so the complex permittivity ε of a metal is practically a purely imaginary number, expressed in terms of the imaginary unit and a real-valued electrical conductivity (, eq.(4.8)-(4.9), p. 122).
Read more about this topic: Relative Permittivity
Famous quotes containing the word metals:
“As in digging for precious metals in the mines, much earthy rubbish has first to be troublesomely handled and thrown out; so, in digging in one’s soul for the fine gold of genius, much dullness and common-place is first brought to light.”
—Herman Melville (1819–1891)
“When human beings have been fascinated by the contemplation of their own hearts, the more intricate biological pattern of the female has become a model for the artist, the mystic, and the saint. When mankind turns instead to what can be done, altered, built, invented, in the outer world, all natural properties of men, animals, or metals become handicaps to be altered rather than clues to be followed.”
—Margaret Mead (1901–1978)