1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

When light reflects from a thin film back toward the source, what is the path length?

  1. Apr 19, 2012 #1
    1. The problem statement, all variables and given/known data

    When light reflects from a thin film back toward the source, what is the path length difference?


    3. The attempt at a solution

    A. It is equal to twice the thickness of the film.
    B. It is equal to the thickness of the film.
    C. It is equal to half the thickness of the film.

    I have rules out C. I think the answer is A but I'm not sure.
     
  2. jcsd
  3. Apr 20, 2012 #2
    Re: When light reflects from a thin film back toward the source, what is the path len

    I'm leaning towards A now. Anyone have any ideas?
     
  4. Apr 20, 2012 #3
    Re: When light reflects from a thin film back toward the source, what is the path len

    Tell us why you are leaning towards A and we can help you evaluate that thought process.
     
  5. Apr 20, 2012 #4
    Re: When light reflects from a thin film back toward the source, what is the path len

    I guess the path length difference is between the rays reflected from the two surfaces of the film. When light reflects from a "thin" film back toward the source, the angle of incidence is approximately 90 degree. So, the optical path length difference is twice the film thickness times the refractive index of the film. One also has to take into account the fact that a phase change of 180 degree occurs upon reflection from an optically denser medium.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: When light reflects from a thin film back toward the source, what is the path length?
  1. Thin Film Reflection (Replies: 1)

Loading...