Medium (optics)

Encyclopedia : M : ME : MED : Medium (optics)

A medium is material through which waves propagate; electromagnetic waves in optics. The permittivity and permeability of the medium define how electromagnetic waves propagate in it. The medium has an intrinsic impedance, given by

:[\eta = \sqrt]

where [\mu] is the permeability of the medium and [\varepsilon] is the permittivity of the medium.

Waves propagate through a medium with velocity [c_w = \nu \lambda ], where [\nu] is the frequency and [\lambda] is the wavelength of the electromagnetic waves. This can also be put in the form

[ c_w = \ ,]

where [\omega] is the angular frequency of the wave and [k] is the wavenumber of the wave. In electrical engineering, the symbol [\beta], called the phase constant, is often used instead of [k].

The propagation velocity of electromagnetic waves in free space, i.e. the absence of a medium, is

[c_w = }\ ,]

where [\varepsilon_0] is the permittivity of free space

:[~ \mu_0 ~] is the permeability of free space.

References

From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.

Medium (optics)

See also

References