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B Are superconductors perfect reflectors?

  1. Jun 3, 2016 #1
    To my current(somewhat pathetic:wink:) knowlege the reflection off metal surfaces happens because
    the changing electric and magnetic fields cause "mini currents" or charge redistributions
    which produce their own electromagnetic waves identical to the incoming ones or in other words the reflection.

    My guess is that resistance and the fact that metals really aren't a continuous sea of charge (but more like a few electrons moving fairly freely in a crystal lattice) make the reflective abilities of metals less than perfect.

    But how close do you get with a superconductor?
    Maybe it was just the condensation due to the cold temperatures or a little oxidant layer or protective coating but i can't remember superconductors being particularly bright or shiny.:confused:
    And if there is no fundimental misconception about that model of reflection then i would be interested to know where it breaks down.
    The thought that very high gamma ray photons should be reflected off a superconductor is absurd.
    So why doesn't it happen ?
     
  2. jcsd
  3. Jun 3, 2016 #2

    DrSteve

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  4. Jun 4, 2016 #3
    Thanks for the answer.
    I am just a 11 grade student in germany (i would be in high school in america) so i didn't understand very much of that pdf...
    Consequently my question isn't completely resolved.
    I changed my question a little:
    Superconductors aren't perfect reflectors, but they are the better reflectors than any non-superconducting surface.
    Is the statement correct now ?

    In the paper you linked a formula for surface resistivity is derived from page 16 to 18.
    What does that formula imply ?
    Is the absorbed power per reflection proportional to the surface resistivity ?
    And if the resistance of the copper pairs does not arise from interactions with the crystal lattice then where does the dissipated energy go.
    And is the formula only valid in the microwave regime or does the surface resistivity keep rising to the second power of the frequency ?

    Additionaly i assume that the superconductivity has little to no influence on the reflective "abilities" in the optical spectrum.
    When cooling down high temperature superconductors they don't start to look different when they pass their transition temperature.
    Why is that?

    It might be that i am asking the wrong questions.... but i am still quite confused.
    I am very much in the dark concerning this topic so i would be glad about a "beginner"-friendly explaination :smile:.
     
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