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Why silver atoms reflect light?

  1. Feb 24, 2008 #1
    why silver atoms reflect light? why they don't refract it, like the Huygens's principle says?
     
  2. jcsd
  3. Feb 24, 2008 #2
    Well, you need to go quite deep to get the full understanding here.

    In short, your answer would be "plasmons" :)


    The conduction electrons in the metal will start to vibrate longitudinally as a response to the incident EM-radiation (ie the electrons will move back and forth, as a reaction to the incident oscillating electrical field). It is this oscillation of conduction electrons that gives rise to the phase shifted reflected light of a conductor.

    The plasma frequence is that frequence above which the electrons can no longer 'follow' the oscillating incident E-field. This kinda means that the E field is vibrating too fast and the electrons cannot respond anymore to that motion. If this happens, the E field (thus light as well) will no longer be reflected but it will pass through the medium.

    Plasmons are the particles that are associated with the longitudinal waves of the conduction electrons in a metal that has been submitted to incident EM-radiation (just like photons are the particles associated to EM radiation).

    Hope that helps,

    regards
    marlon
     
    Last edited: Feb 24, 2008
  4. Feb 24, 2008 #3
    Isn't the property of reflection of the mirrors, is result of the silver atoms? Are the EM waves released from the atoms, are released in whole directions?
    Thanks.
     
  5. Feb 24, 2008 #4
    What atoms are you talking about ? You don't need to consider atoms individually here. We are talking about metals for example : metals are many particle systems, many atoms interacting with each other. Such systems have different properties like conduction and valence bands which you will not find in the case of individual atoms !

    Basically, metals reflect incident light because of the interaction between the light and the conduction electrons inside the conduction band ! That is what i am talking about.

    marlon
     
  6. Feb 24, 2008 #5
    They absorb the energy, and re-emit it? Do they release the waves in whole directions, like in the Huygen's principle?
     
  7. Feb 24, 2008 #6

    Dale

    Staff: Mentor

    Isolated silver atoms do not reflect light. Silver metal reflects light, and even then only when polished into a nice smooth surface sufficiently large.

    I don't understand your intepretation of Huygen's principle to exclude reflection.
     
  8. Feb 25, 2008 #7
    Why does polishing a metal make it reflective? And I think the question remains, what in the silver metal plate exactly makes it a better reflective metal than, say iron? It is not a better conductor metal I think, so what is the major property of silver that makes it the best substance for mirrors?
     
  9. Feb 25, 2008 #8

    D H

    User Avatar
    Staff Emeritus
    Science Advisor

    You really should look things up first. Silver has the highest conductance of any metal, with more than 6 times the conductivity of iron. Nobody uses iron wiring in their house. It is illegal to do so in many places! We use copper instead. Copper has a conductivity close to that of silver but costs a lot less than silver.
     
  10. Feb 25, 2008 #9
    What the conductivity has to do with reflection? Why the silver atoms reflect 99% of the light which interacts with them. Why glass 96% reflects, and 4% refracts light?
     
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