Absorbance of UV light by glass

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SUMMARY

The discussion focuses on the absorbance of UV light by glass of varying thickness, specifically using the Beer-Lambert Law to understand the relationship between absorbance percentage and glass thickness. Participants suggest that the absorbance will plateau at a certain thickness, indicating that UV light can still cause sunburn through glass. Key concepts include the absorption coefficient (α) and the extinction coefficient (κ), which are critical for calculating light absorption in glass. The extinction coefficient for soda lime glass is referenced, although its accuracy for UV light is questioned.

PREREQUISITES
  • Understanding of the Beer-Lambert Law
  • Familiarity with absorption coefficient (α) and extinction coefficient (κ)
  • Basic knowledge of UV light properties
  • Concept of light absorption in materials
NEXT STEPS
  • Research the Beer-Lambert Law in detail
  • Investigate the extinction coefficients of various glass types for UV light
  • Explore experimental methods for measuring light absorbance in glass
  • Learn about the effects of glass thickness on UV light transmission
USEFUL FOR

Students conducting investigations on light absorption, physics educators, and anyone interested in the optical properties of materials, particularly in relation to UV light and glass.

N0b0dy
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Hi, I'm doing an investigation into the absorbance of UV light by glass of varying thickness (constant density and standard type of glass) for an assigment. However, we're not actually supposed to carry out the investigation due to time constraints, so we're meant to make up the numbers ourselves. This would be easy if I was doing a topic such as projectile motion. However, in this case I have literally no idea what figures I should include. Could anyone please help get me started by suggesting some increments of glass thickness that would demonstrate a particular relationship? I assume the graph (absorbance % against glass thickness) would plateau off at a certain point because I've heard many people say that you can still be sunburnt no matter what kind of glass it is.
 
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Since this is homework, rather than give you the answer, I'll just give you a few hints:

The Beer-Lambert Law, or Beer's Law, or a few other permutations deals with absorption of light through a medium as the light passes through said medium:
http://en.wikipedia.org/wiki/Beer-Lambert_law

You'll note that one of the formulations involves the absorption coefficient \alpha which is elaborated on further down in the article. Part of that elaboration is the extinction coefficient \kappa.

The extinction coefficient of some glasses (including plain-jane soda lime glass) is given here (no idea whether or not they're right, however):
http://www.colostate.edu/orgs/SEAL/research/IAM/iamv2/manual.txt

Keep in mind that this is probably for a visible colour, and when dealing with real glass and UV light, the approximation given for absorption coefficient is probably going to differ a fair bit from the 'real' value (which I can't easily find anywhere on the internet)

EDIT: Disclaimer, I am not an optics guy.
 
Last edited by a moderator:
MATLABdude said:
Since this is homework, rather than give you the answer, I'll just give you a few hints:

The Beer-Lambert Law, or Beer's Law, or a few other permutations deals with absorption of light through a medium as the light passes through said medium:
http://en.wikipedia.org/wiki/Beer-Lambert_law

You'll note that one of the formulations involves the absorption coefficient \alpha which is elaborated on further down in the article. Part of that elaboration is the extinction coefficient \kappa.

The extinction coefficient of some glasses (including plain-jane soda lime glass) is given here (no idea whether or not they're right, however):
http://www.colostate.edu/orgs/SEAL/research/IAM/iamv2/manual.txt

Keep in mind that this is probably for a visible colour, and when dealing with real glass and UV light, the approximation given for absorption coefficient is probably going to differ a fair bit from the 'real' value (which I can't easily find anywhere on the internet)

EDIT: Disclaimer, I am not an optics guy.
So there's not really any practical way of working this out unless I actually carry through with the experiment? This is high school standard so I assume I don't need to go into such great detail. Could anyone provide me with a hint as to when the absorbance plateaus off which I can base my 'results' on?
 
Last edited by a moderator:

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