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Need help with spacing between slits

  1. Mar 30, 2008 #1
    1. The problem statement, all variables and given/known data
    Light from a helium-neon laser (λ=590 nm) is used to illuminate two narrow slits. The interference pattern is observed on a screen 3.42 m behind the slits. Twelve bright fringes are seen, spanning a distance of 47 mm. What is the spacing (in mm) between the slits?

    2. Relevant equations

    3. The attempt at a solution
    t = wavelength

    t= 590 nm
    L = 3.42 m
    y = 47 mm
    12 fringes
    so the space between 2 fringes would be 47mm/11 = 4.27 mm

    d = tL/y = 4.73 x 10^-4 m

    I don't have the answer to this problem so is this the right way to do this???
  2. jcsd
  3. Mar 30, 2008 #2
    Does anyone know if this is right?
  4. Mar 30, 2008 #3
    your variables are a bit confusin. try labeling them. also, are you saying that the light is coming straight out? (because light doesn't usually stay in a straight beam, does it)
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