How a mirror works: condensed matter explanation

In summary, the conversation revolves around the question of how mirrors work at the atomic level and the possible explanations for it. The main points discussed are the collective interaction of light with atoms in the material, the Lorentz model of dielectric function, and the role of free electrons in metals. The conversation also mentions references for further information on this topic.
  • #1
haushofer
Science Advisor
Insights Author
2,962
1,508
TL;DR Summary
fed up with phenomenological explanation of mirrors, need fundamental explanations
Dear all,

in the context of my teaching I was wondering what exactly the explanation is of how a mirror works at the atomic level. Apparently, the fact that reflecting materials are often also good conductors and hence big energy bands helps reflecting the photons. Does someone know a nice set of lecture notes where this is explained? So, questions like:

* how does the elecotromagnetic field / photons interact with the reflecting material as a solid state as a whole
* how exactly does the ability to reflect depend on the atomic structure of the material
* how can the law of reflection be explained within the "atomic paradigm" (instead of the maxwell- field approach)
* how does solid state physics explain the difference between reflecting materials and non-reflecting materials?
* do the photons interact with the free electrons of the material, or also with the bound ones from the atoms?

Well, hopefully you get the idea of my question. Of course, answers will also be appreciated :) Greetings!

sidenote: I'm a theoretical physicist who has forgotten most of his solid state physics...
 
Physics news on Phys.org
  • #2
Light wavelengths are around 5000 angstroms, and atoms are about an angstrom, so there are tens of millions of atoms responding at any instant to the EM fields of the wave. An atomic explanation is the wrong picture, as the light interacts collectively.

Some discussion in another context here.
 
  • Like
Likes Cryo and BvU
  • #4
Vanadium 50 said:
Light wavelengths are around 5000 angstroms, and atoms are about an angstrom, so there are tens of millions of atoms responding at any instant to the EM fields of the wave. An atomic explanation is the wrong picture, as the light interacts collectively.

Some discussion in another context here.
Thanks. I also had the idea that the picture of one single photon being absorbed and re-emitted (reflected) by a single electron is troublesome. Do you know of any references which cover this stuff in a pedagogical way?
 
  • #5
Feynman !
 
  • #6
Vanadium 50 said:
Light wavelengths are around 5000 angstroms, and atoms are about an angstrom, so there are tens of millions of atoms responding at any instant to the EM fields of the wave. An atomic explanation is the wrong picture, as the light interacts collectively.

I disagree with the second sentence. The Lorentz model of the dielectric function is often explained in the context of the polarization of an atom. In fact, it is possible to perfectly fit the optical phonons of insulators (provided the phonons aren't anharmonic) with the Lorentz model. These oscillations are usually <200 meV and the IR wavelengths needed approach 1 millimeter.
 
  • #7
haushofer said:
Summary:: fed up with phenomenological explanation of mirrors, need fundamental explanations
You have so many questions, but I don't want to answer them all at once. I don't know if you've gone through them yet, but Milli Dresselhaus's notes are very detailed so you may get lost in it all.

The short answer to why mirrors work is that, in metals, the free electron density is high enough and the scattering is low enough that the free electrons form a plasma with a high reflectivity up to the plasma frequency.

Regarding what you said about bands: everything with charge in a material effects the reflectivity, but broad bands are not the reason why metals have high reflectivity.
 

Related to How a mirror works: condensed matter explanation

1. How does a mirror reflect light?

A mirror reflects light through a process called specular reflection. This means that the light rays hitting the mirror's surface bounce off at the same angle they hit it, creating a clear and accurate reflection.

2. What is the material used to make mirrors?

The most common material used to make mirrors is glass, specifically a type of glass called float glass. This type of glass is coated with a thin layer of metal, usually aluminum or silver, to create the reflective surface.

3. Why do mirrors appear to reverse images?

Mirrors appear to reverse images because of the way light is reflected off of them. When light hits the mirror, it bounces off at the same angle it came in, but in the opposite direction. This creates the illusion of a reversed image.

4. How does the thickness of a mirror affect its reflection?

The thickness of a mirror does not affect its reflection. As long as the reflective coating is intact, the mirror will reflect light the same way regardless of its thickness. However, thicker mirrors may be more durable and less likely to break.

5. Can mirrors be made to reflect different colors?

Yes, mirrors can be made to reflect different colors by using a different type of metal coating. For example, a gold-coated mirror will reflect a golden color, while a copper-coated mirror will reflect a reddish-orange color. These colors are created by the selective absorption of certain wavelengths of light by the metal coating.

Similar threads

  • Atomic and Condensed Matter
Replies
1
Views
2K
  • Atomic and Condensed Matter
Replies
7
Views
2K
  • Science and Math Textbooks
Replies
7
Views
2K
  • Atomic and Condensed Matter
Replies
22
Views
6K
  • Atomic and Condensed Matter
Replies
2
Views
1K
  • Atomic and Condensed Matter
Replies
10
Views
2K
Replies
15
Views
723
  • STEM Academic Advising
Replies
1
Views
1K
  • Atomic and Condensed Matter
2
Replies
36
Views
7K
  • Advanced Physics Homework Help
Replies
1
Views
346
Back
Top