What will happen on absorbance/transmittance if the refractive index of material increases?
Usually, when the refractive index increases the transmittance decreases and vice versa.
The spectral dependence of the refractive index is closely related to the spectral dependence of the absorbance through the Kramers-Krönig relationships
One consequence is that if you have a strong absorption feature, you will have a high refractive index even in the transparency region (i.e. out pf resonance)
In light matter interaction material have indices are in complex form. Real part is refractive index and imaginary part is absorptive index. Both parameters effect the transmittance but absorbance only due to absorptive coefficient. Effect of refractive index on transmittance have only at interface of two different mediums or when density of meadium changing in light propagation direction. Absorption present only when meadium axcited at resonance
Refractive index is a ratio of the speed of light through a medium with reference to another medium, at a given wavelength. How does absorption even come into the picture?
In general the refractive index is a complex variable, with the real part representing refraction (i.e. changes in the speed of light), and the imaginary part absorption (chances in amplitud and therefore irradiance), that is the relationship. Both are functions of wavelength(frequency), but not the same function, nor arbitrarily different functions either. The principle of causality establishes a precise relation between both wavelength dependencies through the Kramers-Krönig relationships. You can read this in standard Electromagnetics textbooks such as Panofski and Philips, or Fowles' Introduction to Modern Optics
In case non-linear optical materials, what is the actual relation between degree of crystalline nature - refractive index-dielectric constant?????.
Hello ,
If you have transmittance data, first you need to calculate the absorption
coefficient (alpha-a)
alpha = 2.303 log (1/T)/t where t-thickness of the sample
then, reflectance(R) in terms of absorption
coefficient (alpha-a)
R = (exp(−at)+(or)-((exp(−at)T -exp(-3at)T+exp(-2at)T2)1/2)/exp(−at)+exp(-2at)T
then
n = (-(R + 1)+(or)- 2R1/2)/R-1
where n is refractive index
I hope this information may help you.
Regards,
Aravind Rudrarapu
Thanks for the question. Really something still is not clear. Assume that you have a red liquid which is absorbing green light. If you leave it in one arm of a Michelson interferometer and if you gradually increase the concentration of the absorbing dye, what happens to the interference fringes. In the other words what happens to the refractive index of the medium.
We have an absorbing medium and assume that the wavelength of the green laser light which is used in interferometer is at the absorption peak of the dye liquid. Off course the transmitted light is that which is not absorbed, but what refractive index the light feels by passing through the liquid and how can it be explained by dispersion relation and anomalous dispersion.
The influence of refractive index change on the transmittance or the absorbance has different behaviors if the sample was treated as a bulk material or was prepared in thin film, so this point should be taken in consideration.
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