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Homework Help: Reflected white light, thin transparent coating on glass

  1. Apr 17, 2007 #1
    1. The problem statement, all variables and given/known data

    Suppose a reflected white light is used to observe a thin transparent coating on glass as the coating material is gradually deposited by evaporation in a vacuum, Describe color changes that might occur during the process of building up the thickness of the coating


    2. Relevant equations



    3. The attempt at a solution
    im not sure
     
  2. jcsd
  3. Apr 17, 2007 #2
    The interference of waves reflected from the opposite surface of the film would cause a band of colors to be formed in the film.
    Is this correct?
     
  4. Apr 17, 2007 #3
    I think you should describe the geometry with more precision. (my feeling)
    Do you mean a collimated beam shining with some angle on the thin film?
    Or maybe it is a point source of white light illuminating the whole film?
    How is the reflexion observed?
    I think these links could be useful:
    http://en.wikipedia.org/wiki/Anti-reflective_coating
    http://en.wikipedia.org/wiki/Fresnel_equations
    The derivation of the Fresnel laws in an EM course could be instructive.
    Finally, you should ask yourself the question: why would different colors behave differently in the reflexion? What is the reason?
    I could not find the full theory of the thin film on the web, you should try.
     
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