Interaction of EM radiation with Glass

In summary: The answer to your question is that lead has a large nucleus which gives it a high positive charge and this makes it difficult for gamma rays to remove electrons from the atom. This is why lead attenuates gamma rays so well.
  • #1
Jimmy87
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Hi,

I wanted some clarification on the mechanism for how EM radiation interacts with standard glass, namely IR, visible and high energy (UV and X-ray).

Looking online most sources seem to say the band gap is around 10eV. Since visible light is about 1-3eV visible light will be transmitted.

IR however has a much lower energy yet is absorbed. Is this because you need to consider surface lattice vibrational modes instead of band gap theory. In that these vibrational modes of the lattice match the frequency of IR and are therefore absorbed?

Regarding UV is it right to now consider the band gap again in that UV has energies beyond the band gap of 10eV and will be absorbed by electrons in the ground state? Sources online say that some UV can penetrate glass and hence cause sun burn. Looking online I have found ranges for UV from 3-130eV so is it the UV photons between 3-10eV that get transmitted.

I also wondered how X-ray and gamma photons would interact with glass?

Thanks for any insights. This is just general curiosity and interest.
 
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  • #2
Jimmy87 said:
I also wondered how X-ray and gamma photons would interact with glass?
My best guess is that x-ray and gamma ray photons would either pass right through without much interaction, undergo an absorption where multiple electrons are ionized from their atoms from the very high amount of energy deposited, or they would scatter off of atoms in the glass in some fashion. I doubt glass is going to absorb many photons once you get into the x-ray range and beyond, so it is probably highly transparent in that part of the spectrum (as most things are).
 
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  • #3
Where did @MeadowZ detailed answer go?

Does anyone know any detailed information about how high energy EM radiation interacts with lead glass that is used to block EM radiation like gamma whilst still being transparent to optical light.

I can only find this article in terms of band gap:https://www.tandfonline.com/doi/abs/10.1080/00207218908921075?journalCode=tetn20

Does adding lead to the glass change the band gap? Is band gap theory anything to do with how gamma interacts with lead glass or would it be a different mechanism? As @Drakkith said it would like cause a scattering or emission of an electron with regular glass so I’m keen to know the mechanism in lead glass? Thanks
 
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  • #4
Glass becomes opaque just past the visible. Quartz goes a little farther.

The interactions of x- and gamma rays with glass is little different than from sand or other forms of silicon oxides.
 
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  • #5
Jimmy87 said:
Is band gap theory anything to do with how gamma interacts with lead glass or would it be a different mechanism?
I don't know much about high energy radiation but gamma rays have energies of several MeV and band gaps are measured as several eV so the mechanism is very different. I think the interaction of the gamma with Pb nucleus will produce a shower positrons and electrons and other ionizing radiation that scatter like bowling pins in the alley.
 
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  • #6
Jimmy87 said:
Where did @MeadowZ detailed answer go?
That answer was detailed but also vapid - plausible-sounding prose wrapped around a spam link to a “study help” web site. After several such posts in several threads it became clear that they were here to spam.

It’s best not to think too much about what happens to spammers…. Let’s just say that the problem has been taken care of.
 
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  • #7
Nugatory said:
It’s best not to think too much about what happens to spammers
Oh...and make it look like an accident.
 
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  • #8
Nugatory said:
That answer was detailed but also vapid - plausible-sounding prose wrapped around a spam link to a “study help” web site. After several such posts in several threads it became clear that they were here to spam.

It’s best not to think too much about what happens to spammers…. Let’s just say that the problem has been taken care of.

That’s not good. Was weird how it was the same as my post just with a few bits edited out.
 
  • #9
hutchphd said:
I don't know much about high energy radiation but gamma rays have energies of several MeV and band gaps are measured as several eV so the mechanism is very different. I think the interaction of the gamma with Pb nucleus will produce a shower positrons and electrons and other ionizing radiation that scatter like bowling pins in the alley.
Ah yes of course it is in eV. Are the only EM radiations that interact with band gap theory just visible and UV then? IR by lattice vibrational excitations and high energy through scattering and ionisation?

I have been looking for an answer as to why lead attenuated gamma so well. It was explained by lead having a large nucleus which also gives it a large positive charge due to the high number of protons. Therefore, electrons are harder to remove from the atom hence it can cause a large reduction in energy of the incoming gamma photon?
 
  • #10
Jimmy87 said:
I have been looking for an answer as to why lead attenuated gamma so well.
First, random words by a spammer to cover their spam is unlikely to help.

What do you mean by "so well"? Radiation length is 27 g/cm2. That's between sau lead at 5 and carbon at 42.
 
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  • #11
I don't know all the answers but I think in the final analysius at these energies the important factor is mass density (and cost). I have worked on some designs for medical devices that use Tungsten (Wolfram) instead of lead because of size (mass density 1.7 times that of lead). Actutally I think the prototype used W because the original design size was too damned small. Nothing magic about lead so far as I know, although it is at the end of most nuclear decay chains.
 
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  • #12
It's mostly electron density. High Z helps and high physical density helps.
 
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  • #13
So the mass density is really just an indicator for the electronic (volume) density? Interesting idea...didn't think of that.
 
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  • #14
X-ray photons should have small enough wavelength to scatter (diffract) in the lattice
https://en.wikipedia.org/wiki/Bragg's_law
https://ceramics.org/wp-content/uploads/2009/03/warren_x_ray1.pdf

Gamma-ray photons should have enough energy to interact with the electron and the protons, and we could get say photo-pairproduction of electron and positrons, compton scattering and so on.
https://www.sciencedirect.com/science/article/abs/pii/S0029549316302539
https://www.nature.com/articles/s41598-022-07450-7
 
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  • #15
Vanadium 50 said:
It's mostly electron density. High Z helps and high physical density helps.
Say you irradiate a quantity of liquid diprotium vs. equal quantity of liquid dideuterium.
At triple point (14 K), diprotium is 77,2 g/l, which makes 38,6 mol/l. Dideuterium is 162,4 g/l, which makes 40,6 mol/l... about 5% more.
Does deuterium have over twice the absorption of protium, or only 5% more due to lower molar volume?
 

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