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Slit width

  1. Apr 24, 2009 #1
    1. The problem statement, all variables and given/known data

    The central bright fringe in a single slit diffraction pattern from light of wavelength 412 nm is 1.9 cm wide on a screen that is 1.05 m from the slit.

    How wide is the slit?

    2. Relevant equations

    i keep trying the equation .5asintheta=.5wavelength
    I cant seem to get the right answer but im sure its easy

    3. The attempt at a solution
     
  2. jcsd
  3. Apr 24, 2009 #2

    Doc Al

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    Staff: Mentor

    Express sinθ in terms of pattern position and distance to screen. (Use a small angle approximation.)
     
  4. Apr 24, 2009 #3
    is it the eq. tantheta=h/D?
     
  5. Apr 24, 2009 #4

    Doc Al

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    Staff: Mentor

    Yes, and for small angles tanθ ≈ sinθ.
     
  6. Apr 24, 2009 #5
    do you use h=1.9 cm and D=1.05m?
     
  7. Apr 24, 2009 #6

    Doc Al

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    Staff: Mentor

    Not exactly. Note that in the diffraction equation, "h" is measured from the central maximum.

    Also, when you wrote ".5asintheta=.5wavelength" why do you have .5 in there?

    Read this: http://hyperphysics.phy-astr.gsu.edu/HBASE/PHYOPT/sinslit.html" [Broken]
     
    Last edited by a moderator: May 4, 2017
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