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Thin Film Interference and wavelength

  1. Feb 8, 2014 #1
    1. The problem statement, all variables and given/known data
    Light of wavelength 550 nm in air is normally incident on a glass plate (n=1.5) whose thickness is 1.1 X 10^-5 m. (a) What is the thickness of the glass expressed in terms of the wavelength of light in glass?(b) How many reflected waves will experience the 180 degree phase shift? c) Will the reflected waves interfere constructively or destructively?

    2. Relevant equations

    t min = λ / 4n1

    3. The attempt at a solution
    I'm really not sure where to begin with this one. Here's what I have:

    λm = 550 nm / 1.5 =366.6 nm ~ 360 nm

    1.1 x 10 ^ -5 = 360 / 1.5

    This doesn't make sense. Could someone please point me in the right direction? Thank you!
  2. jcsd
  3. Feb 9, 2014 #2


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    Homework Helper

    You are right, the wording of the problem doesn't make sense.

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