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Thin film interference - Minimum thickness

  1. May 11, 2013 #1
    1. The problem statement, all variables and given/known data
    A lens (##\mu##=1.5) is coated with a thin film of refractive index 1.2 in order to reduce the reflection from the surface at ##\lambda=480 nm##. Find the minimum thickness of the film which will minimize the intensity of reflected. [Assume near normal incidence]


    2. Relevant equations



    3. The attempt at a solution
    I don't really know how to begin with this. It looks to me that this is related to thin film interference but I have never dealt with three different mediums while solving problems related to this.
     
  2. jcsd
  3. May 11, 2013 #2

    Doc Al

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    Staff: Mentor

    It's just thin film interference. All you need to worry about are the reflections from the top and bottom surfaces of the film.
     
  4. May 11, 2013 #3
    Is it simply a plug and chug question then? :tongue2:

    I get the right answer using the formula ##2\mu d=(n+1/2)\lambda## and putting ##n=0##. I get ##d=10^{-7} m##. Thanks Doc Al! :smile:
     
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