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Fresnel Biprism Equation Derviation- please help

  1. Nov 13, 2004 #1
    Fresnel Biprism Equation Derviation- please help!!

    I recently did the Fresnel Biprism Experiment in order to calculate the wavelength of sodium light. As part of my write up I am to show the derviation of the formula d = (d1 * d2)^1/2 where d = actual separation of the virtual slits. Basically I dont have any idea how to derive this, all I know that it is supposed to come from the simple lens formula......does anyone have any idea how to derive this?? Any help would be greatly appreciated!!
    Last edited: Nov 13, 2004
  2. jcsd
  3. Nov 13, 2004 #2


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    I am looking at http://www.uow.edu.au/eng/phys/200labs/phys215/fresnel.pdf [Broken]

    The separation of the images at a given lens position is related to the separation of the virtual sources like the ration of image to object distances.

    Let u = image distance
    let v = object distance

    In the first lens position you have

    [tex] \frac c {c_1} = \frac u v [/tex]

    At the second lens position you have
    [tex] \frac c {c_2} = \frac v u[/tex]

    Can you work it out from there?
    Last edited by a moderator: May 1, 2017
  4. Nov 13, 2004 #3
    Thanks, I just didnt really know where to start, but looking at that it helps a lot, as I know where to work from. Thanks again!
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