Refractive index in the ultraviolet region

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Discussion Overview

The discussion revolves around the behavior of refractive index in the ultraviolet (UV) region of the electromagnetic spectrum, particularly in relation to its behavior compared to optical and X-ray regions. Participants explore the relationship between wavelength, frequency, and refractive index, as well as the absorption characteristics of materials in these regions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that shorter wavelengths, such as blue light, experience stronger refraction, while X-rays are not refracted by glass, leading to questions about the behavior in the UV region.
  • Another participant challenges the claim that X-rays go straight through glass, stating that X-rays are absorbed by materials due to electronic transitions, particularly in the XUV and X-ray regions.
  • It is proposed that the refractive index profile is influenced by the medium's structure and that strong absorption can occur in the UV region, which is linked to anomalous dispersion where absorption peaks are present.
  • A participant acknowledges their earlier inaccuracy regarding X-ray behavior, clarifying that while X-rays can be refracted at media boundaries, the refractive index in that region is typically very close to unity, resulting in minimal deflection compared to visible light.
  • A request for examples of graphs depicting refractive index versus frequency is made, indicating a desire for visual representation of the discussed concepts.

Areas of Agreement / Disagreement

Participants express differing views on the interaction of X-rays with glass, with some asserting that X-rays are absorbed while others emphasize their minimal deflection. The discussion remains unresolved regarding the exact behavior of refractive index in the UV region and its relationship to absorption and dispersion.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the interaction of X-rays with materials and the specific conditions under which refractive index behavior is analyzed. The dependence on material properties and the definitions of terms like "absorption" and "refraction" are not fully explored.

Gruxg
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When white light is refracted in a prism, we can see that blue color has the strongest refraction: the shorter the wavelength, the strongest the refraction. But the electromagnetic radiation with very short wavelength (X-rays) are not refracted by an amorphous solid such as glass: most part of the radiation goes straight through the glass with no interaction.

Since the behaviour is so different in the optical and the X-ray regions, I wonder what happens between both, i.e, in the UV region. Does the refractive index increase with the frequency of the wave until some point and then fall quickly, or what happens exactly?

Thanks in advance!
 
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Gruxg said:
most part of the radiation goes straight through the glass with no interaction.
This is in most cases not true, X-rays are well known to be easily absorbed by common medium, the absorption is due to the electronic transition in the medium that typically takes place within XUV and X-rays region.
Gruxg said:
Since the behaviour is so different in the optical and the X-ray regions, I wonder what happens between both, i.e, in the UV region. Does the refractive index increase with the frequency of the wave until some point and then fall quickly, or what happens exactly?
The refractive index profile is determined by the structure (e.g. the bonding types, crystal properties etc) of the medium, where there are transitions in the level structure, there can be found strong absorption. One of such regions is the UV region as explained above. Now absorption and refractive index are mutually-dependent quantity, in particular it can be shown that whenever there is an absorption peak, there will also be a region where anomalous dispersion takes place. In the refractive index graph vs frequency, anomalous dispersion is shown as a negative slope region.
 
OK, I was inaccurate when I said that "most part of the radiation goes straight through the glass with no interaction", but I meant that the part of the X-ray beam that is transmitted through the glass (not absorbed or scattered) goes straight, does not undergoes any "deflection" like the light refracted in the prism. But I have just found out that X-rays can be refracted in the boundary between two media, it's just only that the refractive index is typicaly very very close to unity in that region of the spectrum and the deflection is tiny compared to ordinary light refraction.

Could you attach or link any example of these graphs?
Thank you!
 
Last edited:

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