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Wavelength nature of light: magnesium Fluoride

  1. Jul 19, 2003 #1

    Dx

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    Hi!

    In terms of magnesium fluoride what is the minimum thickness of mag fl coating that must be applied to a glass lens to make it non-reflecting for that wavelength? (the index of refraction of magnesium fluoride is intermediate to that of air and glass)

    1/2 wavelength out of phase to eliminate reflection. why is this wrong? I usd the formula t = [lamb] / 4n. I used the minimum thickness (m=0) since the destructive interference will occur over the widest angle. Plz help? Or it this a trick question and there is no minimum thickness, huh?
    Dx :wink:
     
  2. jcsd
  3. Jul 19, 2003 #2

    Tom Mattson

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    Obviously, they mean the minimum nonzero thickness. "Zero thickness" means that there is no film at all.
     
  4. Jul 19, 2003 #3

    Dx

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    Re: Re: Wavelength nature of light: magnesium Fluoride

    Its not that obvious Tom since thats not one of the answers. I understand what your saying so I need to figure out the different wavelengths then, huh?
    Dx :wink:
     
  5. Jul 19, 2003 #4
    You are right. The minimum thickness of the coating is given by t=[lamb]/4n. I think you did an error in calculations. Check it please.
     
  6. Jul 20, 2003 #5

    Tom Mattson

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    OK, sorry. I didn't know what m was, and I thought you chose the thickness to be zero.
     
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