Absorbance of UV light by glass

In summary, the author is doing an investigation on the absorbance of UV light by glass of varying thickness but is not able to do the experiment due to time constraints. The author is looking for someone to help them start the experiment by providing increments of glass thickness that would demonstrate a particular relationship. The author is not an optics guy and does not know the figures for absorption coefficient. The author provides a few hints on the Beer-Lambert Law and extinction coefficient. The author asks for someone to provide a hint on when the absorbance plateaus off which the author can base their 'results' on.
  • #1
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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  • #2
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 [itex]\alpha[/itex] which is elaborated on further down in the article. Part of that elaboration is the extinction coefficient [itex]\kappa[/itex].

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.
 
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  • #3
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 [itex]\alpha[/itex] which is elaborated on further down in the article. Part of that elaboration is the extinction coefficient [itex]\kappa[/itex].

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?
 
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1. What is the mechanism behind the absorbance of UV light by glass?

The absorbance of UV light by glass is due to the presence of metal ions, such as iron or copper, in the glass composition. These metal ions absorb UV light and then release it as heat, preventing it from passing through the glass.

2. How does the thickness of glass affect its absorbance of UV light?

The thicker the glass, the more UV light it will absorb. This is because the metal ions have a longer path to travel through the glass, giving them more opportunities to absorb the UV light.

3. Can different types of glass absorb UV light differently?

Yes, different types of glass can have varying levels of UV absorbance depending on their composition. For example, borosilicate glass has a lower absorbance of UV light compared to regular soda-lime glass.

4. What factors can affect the absorbance of UV light by glass?

Apart from the type and thickness of glass, other factors that can affect the absorbance of UV light by glass include the wavelength of the UV light, the angle at which the light hits the glass, and the presence of impurities or coatings on the glass surface.

5. How is the absorbance of UV light by glass measured?

The absorbance of UV light by glass can be measured using a spectrophotometer. This instrument measures the amount of light transmitted through a sample of glass and compares it to the amount of light transmitted through a reference material, giving a numerical value for the absorbance.

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