NationMaster - Encyclopedia: Optical medium

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 Electromagnetic radiation is a propagating wave in space with electric and magnetic components. ... Table of Opticks, 1728 Cyclopaedia Optics (appearance or look in ancient Greek) is a branch of physics that describes the behavior and properties of light and the interaction of light with matter. ... Permittivity is a physical quantity that describes how an electric field affects and is affected by a dielectric medium and is determined by the ability of a material to polarize in response to an applied electric field, and thereby to cancel, partially, the field inside the material. ... Permeability has several meanings: In electromagnetism, permeability is the degree of magnetisation of a material in response to a magnetic field. ...

$eta = sqrt{mu over varepsilon}$

where $μ$ is the permeability of the medium and $varepsilon$ is the permittivity of the medium.

Waves propagate through a medium with velocity $c w = νλ$ , where $ν$ is the frequency and $λ$ is the wavelength of the electromagnetic waves. This can also be put in the form Sine waves of various frequencies; the lower waves have higher frequencies than those above. ... The wavelength is the distance between repeating units of a wave pattern. ...

$c_w = {omega over k} ,$

where $ω$ is the angular frequency of the wave and $k$ is the wavenumber of the wave. In electrical engineering, the symbol $β$ , called the phase constant, is often used instead of $k$ . Angular frequency is a measure of how fast an object is rotating In physics (specifically mechanics and electrical engineering), angular frequency ω (also called angular speed) is a scalar measure of rotation rate. ... Wavenumber in most physical sciences is a wave property inversely related to wavelength, having units of inverse length. ... This article treats electronics engineering as a subfield of electrical engineering, though this is not typical use in some areas. ...

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

$c_w = {1 over sqrt{varepsilon_0 mu_0}} ,$

where $varepsilon_0$ is the permittivity of free space

$~ mu_0 ~$ is the permeability of free space.

References

Serway, Raymond; Jewett, John (2003). Physics for Scientists and Engineers, 6th edition, Brooks Cole. ISBN 0534408427.

Categories: Optics | Electric and magnetic fields in matter

Results from FactBites:

Optics - MSN Encarta (1213 words)
	In geometrical optics the wave theory of light is ignored and rays are traced through an optical system by applying the laws of reflection and refraction.
	If a light ray that is traveling through one homogeneous medium is incident on the surface of a second homogeneous medium, part of the light is reflected and part may enter the second medium as the refracted ray and may or may not undergo absorption in the second medium.
	If the surface of the second medium is smooth or polished, it may act as a mirror and produce a reflected image.

Optics - MSN Encarta (1564 words)
	If a ray is incident obliquely, then a ray entering a medium with a higher refractive index is bent toward the normal, and a ray entering a medium of lower refractive index is deviated away from the normal.
	To an observer in a less dense medium such as air, an object in a denser medium appears to lie closer to the boundary than is the actual case.
	If rays parallel to the optic axis are incident on a spherical surface, they are reflected or refracted so that they intersect or appear to intersect at a point on the optic axis.

More results at FactBites »

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