1. Limited time only! Sign up for a free 30min personal 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!

Thin film interference

  1. Aug 25, 2008 #1
    1. The problem statement, all variables and given/known data
    An oil film (index of refraction no = 1.48) floating on water (index of refraction nw = 1.33) is illuminated from above by white light at normal incidence. The film is 360.0 nm thick.

    What is the longest visible wavelength that will be strongly reflected?

    What is the longest visible wavelength that will be strongly transmitted?
    2. Relevant equations

    2nt = (m + 1/2)λ--constructive
    2tn = m λ, with m = 0,1,2,...

    3. The attempt at a solution
    since visible range=400 - 700 nanometers
    the longest visible wavelength for constructive interference ...should it be λ=2t/(2+1/2)
    and so for the second question i use the second equation?
    Last edited: Aug 25, 2008
  2. jcsd
  3. Aug 25, 2008 #2


    User Avatar
    Science Advisor
    Gold Member

    Do you know the equation for reflectance? I think if the thickness of the film is 1/4λ then the reflectance is minimum.
  4. Aug 25, 2008 #3
    R= ((n2-n1)/(n2+n1))^2
    is it this one?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Threads - Thin film interference Date
Interference in thin films Dec 11, 2017
Maximum/minimum reflection | Thin-film interference Nov 12, 2017
Thin film interference on water Oct 15, 2017
Thin Film Interference Sep 18, 2017