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!

Light question please help

  1. Jun 19, 2008 #1
    1. The problem statement, all variables and given/known data
    A thin flake of mica (n= 1.58) is used to cover one slit of a double slit interference arrangement. The central point on the viewing screen is now covered by what had been the 9th bright fringe before the mica was used. What is the thickness of mica if light of wavelength 556nm is used? answer in microns

    2. Relevant equations

    3. The attempt at a solution
    n lambda = xb/L
    λ is the wavelength of the light,
    b is the separation of the slits, the distance between A and B in the diagram to the right
    n is the order of maximum observed (central maximum is n=1),
    x is the distance between the bands of light and the central maximum (also called fringe distance), and
    L is the distance from the slits to the screen centerpoint.

    This is the only equation i can find so i assume you use it. Is this correct? and if so can someone give me hints on what values to put in for L and x. please. THANKYOU
  2. jcsd
  3. Jun 20, 2008 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    The path difference when one slit is covered with mica will be slightly different.

    [tex] \frac{xb}{L} = (n-1)t[/tex]

    where t is the thickness of the mica.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?