What is the behavior of photons inside glass?

In summary, the conversation discussed the existence of photons inside a material, specifically glass, when a monochromatic laser beam is directed at its surface. The question of whether photons are replaced by other objects such as polaritons was also brought up. Additionally, the speed of photons inside the material was questioned, with the classical theory predicting a speed of v=c/n and quantum theory offering a different perspective. Two links were provided for further information on the topic.
  • #1
lightarrow
1,965
61
TL;DR Summary
Do photons really exist in glass?
Which speed do they have there?
I'm aware of the numerous threads on the subject "light inside glass" there have been in the past, in case you will indicate me an appropriate one, but I haven't been able to find a clear answer to the questions:

1) Do photons really exist inside a (homogeneous, linear, transparent, refracting index n) material as glass, when, e.g., a monochromatic laser beam of wavelength λ is directed normally on its surface, or are they replaced by more "exotic" objects as "polaritons", etc?

2) If they exists and assuming they are not "absorbed and then emitted again after some delay", which speed do they have? I know classical theory shows that v = c/n, and I've read Feynman's QED ("it's as if photons would go through it with a reduced speed" or something alike) but what does quantum theory predicts of their actual speed?

--
lightarrow
 
Physics news on Phys.org

1. What is the speed of light inside glass?

The speed of light inside glass is significantly slower than its speed in a vacuum. This is due to the interaction of photons with the atoms in the glass, which causes them to slow down.

2. How does the refractive index of glass affect photon behaviour?

The refractive index of glass is a measure of how much the speed of light is reduced when passing through it. This affects photon behaviour by causing them to change direction, or refract, when passing through the glass.

3. Can photons be absorbed by glass?

Yes, photons can be absorbed by glass. This occurs when the energy of the photon matches the energy needed to excite an electron in the glass. The absorbed photon's energy is then converted into heat.

4. How does the thickness of glass impact photon behaviour?

The thickness of glass can affect photon behaviour in two ways. First, thicker glass will cause photons to travel a longer distance, potentially increasing the chance of absorption. Second, thicker glass may also cause more refraction, leading to changes in the direction of the photons.

5. Can photons pass through glass without any interaction?

No, photons cannot pass through glass without any interaction. Even if they do not get absorbed or refracted, they will still experience some scattering as they pass through the glass. This is due to the imperfections and impurities in the glass, which cause the photons to change direction slightly.

Similar threads

  • Atomic and Condensed Matter
Replies
22
Views
5K
  • Atomic and Condensed Matter
Replies
3
Views
2K
  • Atomic and Condensed Matter
Replies
8
Views
9K
Replies
16
Views
1K
  • Introductory Physics Homework Help
Replies
4
Views
1K
  • Atomic and Condensed Matter
Replies
2
Views
3K
Replies
2
Views
1K
  • Introductory Physics Homework Help
Replies
5
Views
2K
Replies
14
Views
3K
  • Introductory Physics Homework Help
Replies
3
Views
4K
Back
Top