Permittivity a function of frequency

In summary, permittivity is a function of frequency in relation to the refractive index. The permittivity of a given media depends on the electric susceptibility of the media, which can be considered a measure of how easily the media is polarised by the application of an external electric field. When an electric field is applied to dielectric media, the media will not polarise instantaneously. In other words, polarisation occurs some time after the electric field was initially applied, this results in a so-called 'phase difference' between the frequency of the applied electric field and the polarisation of the dielectric media.
  • #1
morrobay
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How is permittivity a function of frequency ?
And how is permittivity a function of frequency in relation to the refractive index ?
 
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  • #2
morrobay said:
How is permittivity a function of frequency ?
And how is permittivity a function of frequency in relation to the refractive index ?
The permittivity of a given media depends on the electric susceptibility of the media, which can be considered a measure of how easily the media is polarised by the application of an external electric field. Now in general, when an electric field is applied to dielectric media, the media will not polarise instantaneously. In other words, polarisation occurs some time after the electric field was initially applied, this results in a so-called 'phase difference' between the frequency of the applied electric field and the polarisation of the dielectric media.

The refractive index is defined as the ratio of the speed of light in vacuum to the phase velocity of light in the dielectric media. The phase velocity of light is a function of the permittivity and permeability of the media.

I hope that helps.
 
  • #3
Hootenanny said:
The permittivity of a given media depends on the electric susceptibility of the media, which can be considered a measure of how easily the media is polarised by the application of an external electric field. Now in general, when an electric field is applied to dielectric media, the media will not polarise instantaneously. In other words, polarisation occurs some time after the electric field was initially applied, this results in a so-called 'phase difference' between the frequency of the applied electric field and the polarisation of the dielectric media.

The refractive index is defined as the ratio of the speed of light in vacuum to the phase velocity of light in the dielectric media. The phase velocity of light is a function of the permittivity and permeability of the media.

I hope that helps.

Yes I have both Wikipedia papers on permittivity and one on permeabilty and a classics physics text : Haliday Resnick
I have definitions and equations. Permittivity seems to be quite a flexable term.
I would like an explanation on the specific mechanisms of permittivity as it relates to the refractive index. In particular on the 'phase difference' as it relates to an increasing refractive index with frequency.
I understand that the natural resonance frequency of electrons in the medium corresponds more closely to the higher frequencies in the visable part of the spectrum, resulting in preferential absorption and re emission . And when this re emitted light combines with the incident light the average velocity is lower which increases the refractive index at these wavelenghs.If this is related to the so called 'phase difference' then could you explain the specific mechanism in terms of permittivity.
 

1. What is permittivity?

Permittivity is a measure of how easily a material can be polarized by an electric field. It is a fundamental property of a material that determines its ability to store electrical energy.

2. How is permittivity related to frequency?

Permittivity is a function of frequency, meaning that it changes depending on the frequency of the electric field applied to the material. This is due to the fact that as the frequency of the electric field increases, the material's ability to respond to it also changes.

3. What is the significance of permittivity being a function of frequency?

The fact that permittivity is a function of frequency is important because it allows for the characterization of materials at different frequencies. This is particularly useful in the design of electronic devices that operate at different frequencies, as the permittivity of the materials used can greatly affect their performance.

4. How is permittivity measured as a function of frequency?

Permittivity is typically measured using a device called a dielectric spectrometer, which applies an alternating electric field at different frequencies to a sample of the material. The resulting change in the material's polarization is then measured, allowing for the determination of its permittivity at different frequencies.

5. What are some real-world applications of understanding permittivity as a function of frequency?

Understanding permittivity as a function of frequency has numerous practical applications, including in the design of high-frequency electronic devices, such as cell phones and radar systems. It is also essential in the study of materials used in telecommunications and medical imaging, as well as in the development of materials for energy storage and conversion.

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