Glass Transparency: What Allows Visible Light to Pass Through?

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In summary, glass is able to allow visible light to pass through due to its molecular structure. This structure does not match the energy of visible light, allowing it to go straight through without being absorbed. However, other substances in glass can affect its absorption, such as water strongly absorbing infrared light. Photochromatic lenses use a dye molecule that is broken by UV light, creating loose electrons that can change energy levels and absorb visible light. To be truly transparent, glass must have no dispersion, which can be achieved through techniques such as thermal annealing.
  • #1
live4physics
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What´s glass feature (molecular structure) that allow the visible light bypass it ?
:confused:
Thanks
 
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  • #2
Basically there is nothing to absorb the light.
The electron transitions in glass do not match the energy of visible light and so it goes straight through - the same mechanism that makes water transparent.

Other substances in the glass can change the absorption, water strongly absorbs infrared so to make glass fibre-optic for infrared you have to remove all the water from the molten glass first.
 
  • #3
In the case of photochromatic lens, how the UV rays changes the molecular links between atoms ? are there any electron transitions ?
Thanks.
 
  • #4
live4physics said:
In the case of photochromatic lens, how the UV rays changes the molecular links between atoms ? are there any electron transitions ?
Thanks.

Photochromatic is a dye molecule that gets broken by UV light, this leaves a bunch of bonds with lots of loose electrons that can then change energy levels and absorb visible light.
The clever bit is finding a dye that heals itself when you take it out of UV.
 
  • #5
I have a block of formerly transparent lucite that was irradiated with a 15 MeV electron beam in 1959. It was a dark brown due to F-center dislocation. Now, 50 years later, it is transparent again, due to thermal (room temperature) annealing.

For glass to be truly transparent (no absorption), there can be no dispersion (See Kramers Kronig or dispersion relations). See
http://en.wikipedia.org/wiki/Kramers-Kronig_relations
These also apply to the real and imajinary components of electrical circuits.
 
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Related to Glass Transparency: What Allows Visible Light to Pass Through?

1. What is glass transparency?

Glass transparency is the property of a material that allows visible light to pass through it without being scattered or absorbed.

2. What causes glass to be transparent?

Glass is composed of molecules that are arranged in a regular pattern, allowing light waves to pass through with minimal interference.

3. Does all glass have the same level of transparency?

No, the level of transparency in glass can vary depending on factors such as the composition, thickness, and manufacturing process.

4. Can anything block or reduce the transparency of glass?

Yes, certain coatings or treatments can be applied to glass to alter its transparency, such as tinting or frosted finishes. Additionally, impurities or defects in the glass can also affect its transparency.

5. Is glass the only material with transparency?

No, other materials such as plastics, crystals, and water can also exhibit transparency to different degrees.

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