# Refractive index permittivity permeability relationship quotes

### Question About Magnetic Field's and Refractive index? | All About Circuits

agreement of the resulting axion density with the observed dark-matter density these units, the permittivity and permeability of vacuum are both unity: ϵvac = 1 and µvac = 1. .. The first equation is a modification of the laws of Gauss and Amp`ere in the presence of .. quotes to come with an uncertainty of a factor of 2 –3. The dielectric constant & relative permittivity are key to the operation of A static permittivity is often required because the response of a material is a complex relationship related to the frequency of the applied voltage. D = electric flux density Quote: There are some advantages to being right - you don't have to change. dielectric permittivity of the ambient is positive. composite structure with the real part of its effective refractive index being . The situation is analogous with metamaterials, with the difference that we are free to effective magnetic permeability and wire mesh media with negative effective permittivity, was.

In the X-ray regime the refractive indices are lower than but very close to 1 exceptions close to some resonance frequencies. Since the refractive index of the ionosphere a plasmais less than unity, electromagnetic waves propagating through the plasma are bent "away from the normal" see Geometric optics allowing the radio wave to be refracted back toward earth, thus enabling long-distance radio communications. See also Radio Propagation and Skywave.

Negative index metamaterials A split-ring resonator array arranged to produce a negative index of refraction for microwaves Recent research has also demonstrated the existence of materials with a negative refractive index, which can occur if permittivity and permeability have simultaneous negative values.

The resulting negative refraction i. Ewald—Oseen extinction theorem At the atomic scale, an electromagnetic wave's phase velocity is slowed in a material because the electric field creates a disturbance in the charges of each atom primarily the electrons proportional to the electric susceptibility of the medium.

Similarly, the magnetic field creates a disturbance proportional to the magnetic susceptibility. As the electromagnetic fields oscillate in the wave, the charges in the material will be "shaken" back and forth at the same frequency.

The light wave traveling in the medium is the macroscopic superposition sum of all such contributions in the material: This wave is typically a wave with the same frequency but shorter wavelength than the original, leading to a slowing of the wave's phase velocity. Most of the radiation from oscillating material charges will modify the incoming wave, changing its velocity. However, some net energy will be radiated in other directions or even at other frequencies see scattering.

Depending on the relative phase of the original driving wave and the waves radiated by the charge motion, there are several possibilities: This is the normal refraction of transparent materials like glass or water, and corresponds to a refractive index which is real and greater than 1.

## Refractive index

This is called "anomalous refraction", and is observed close to absorption lines typically in infrared spectrawith X-rays in ordinary materials, and with radio waves in Earth's ionosphere. It corresponds to a permittivity less than 1, which causes the refractive index to be also less than unity and the phase velocity of light greater than the speed of light in vacuum c note that the signal velocity is still less than c, as discussed above.

If the response is sufficiently strong and out-of-phase, the result is a negative value of permittivity and imaginary index of refraction, as observed in metals or plasma. This is light absorption in opaque materials and corresponds to an imaginary refractive index. If the electrons emit a light wave which is in phase with the light wave shaking them, it will amplify the light wave.

This is rare, but occurs in lasers due to stimulated emission. The basic idea of a field theory is that all effects must be local and no action at a distance is possible.

### Refractive index - Wikipedia

So, for the magnetic field to come into being and then to get from the earth to the moon to use your examplethe field starts out as nothing and then begins at a localized point.

This implies a time changing magnetic field which also implies a spatially varying electric field.

RefractiveIndex

You can't have one without the other according to Maxwell's equations. This spatially varying electric field also changes in time because it did not exist a moment ago. The time changing electric field implies a spatially varying magnetic field, and the process propagates out in space in this way.

Hence, the fields need to propagate from one point, to the next, to the next etc. This occurs as as an electromagnetic effect according to Maxwell's dynamic field equations.

### DoITPoMS - TLP Library Dielectric materials - The dielectric constant and the refractive index

According to these equations, any localized effect will propagate at a finite speed. That speed is related to the permeability and the permitivity of the medium. In vacuum, the speed is the speed of light, often called "c" and this is the maximum speed.