Relationship between the refractive index and absorption

In summary, there is a complex relationship between refractive index and absorption, with the real and imaginary components being related through the Kramers-Kronig relation. The intensity of light also plays a role, with the intensity-dependent component known as the Kerr nonlinearity for the real part and saturable absorption for the imaginary part. This information may be useful in applying this concept to geological thin section observations.
  • #1
asdfghhjkl
15
0
Hello,

I was wondering is there a relation between the refractive index of the material and the amount of light the material absorbs (e.g. the higher n means higher absorption)? If so what is then a relation between the intensity of the light and the refractive index?

p.s. I am trying to apply this to some geological thin section observations, thus a simple explanation would be appreciated.

Thank you :)
 
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  • #2
asdfghhjkl said:
Hello,

I was wondering is there a relation between the refractive index of the material and the amount of light the material absorbs (e.g. the higher n means higher absorption)? If so what is then a relation between the intensity of the light and the refractive index?

p.s. I am trying to apply this to some geological thin section observations, thus a simple explanation would be appreciated.

Thank you :)
There is no relation between the intensity of light and the refractive index.Refractive index depends on the speed of light through the medium.It varies with wavelength too.
 
Last edited:
  • #3
Ok, thank you.
 
  • #4
asdfghhjkl said:
Ok, thank you.
Please give thanks by using the "thanks" button. :biggrin:
 
  • #5
There is a relation between absorption and refractive index which is known as Kramers Kronig relation:
http://www.rp-photonics.com/kramers_kronig_relations.html
However, to deduce the one from the other, you need to know the absorption or refractive index ideally for all frequencies.
 
  • #6
asdfghhjkl said:
Hello,

I was wondering is there a relation between the refractive index of the material and the amount of light the material absorbs (e.g. the higher n means higher absorption)? If so what is then a relation between the intensity of the light and the refractive index?

Echoing DrDu, absorption is often modeled by allowing the refractive index to be complex-valued (say n = η + iκ) the real part η is the 'refractive' component and the imaginary part κ the 'absorption' component. The components are not independent but related through the Kramers-Kronig relation.
 
  • #7
The intensity-dependent component of the refractive index is known as the Kerr nonlinearity (real part) and saturable absorption (imaginary part).

Claude.
 

1. What is the refractive index?

The refractive index is a measure of how much light is bent or slowed down when passing through a material. It is defined as the ratio of the speed of light in a vacuum to the speed of light in the material.

2. How is the refractive index related to absorption?

The refractive index is directly related to absorption. As the refractive index increases, the amount of light that is absorbed also increases. This means that materials with a higher refractive index will have a higher absorption of light.

3. What is the relationship between the refractive index and the wavelength of light?

The refractive index is inversely proportional to the wavelength of light. This means that as the wavelength of light increases, the refractive index decreases. This is known as dispersion and is the reason why different colors of light bend at different angles when passing through a prism.

4. How does the refractive index affect the speed of light?

The refractive index determines the speed of light in a material. As the refractive index increases, the speed of light decreases. This is because the higher the refractive index, the more interactions and delays the light experiences as it travels through the material.

5. What factors can influence the relationship between the refractive index and absorption?

The relationship between the refractive index and absorption can be influenced by various factors such as the chemical composition of the material, temperature, and pressure. Additionally, the energy level of the material's electrons and the frequency of light can also impact this relationship.

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