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Diffraction Slit Problem Stuck

  1. Apr 19, 2009 #1
    1. The distance between two slits is 0.0500 nm and the distance to the screen is 2.50 m. What is the spacing between the central bright fringe and the first-order fringe? Use yellow light with a wavelength of 580.0 nm. Answers: a. 0.010m b. 0.029m c. 0.290m d. 0.10m
    e. 0.6m

    2. y =LtanΘ
    dsinΘ=mλ for bright fringes

    3. Use dsinΘ=mλ to find Θ and then use Θ to find y with y =LtanΘ.
    I converted 580.0 nm to 5.8 x 10^-7m and 0.50nm to 5.0 x 10^-11m.
    I assumed that d is distance b/t two slits being 5.0 x 10^-7m and that L was 2.5m, the distance to the screen.
    Rearranging the dsinΘ=mλ I find that

    Θ=sin^-1 (m(λ/d))

    giving me

    Θ=(1)(5.8 x 10^-7/5.0 x 10^-11)

    but it doesn't work because -7>-11 right?... so then ... I'm not sure which step I got wrong.. or if my logic is completely off.
  2. jcsd
  3. Apr 19, 2009 #2


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    The value d in not correct because sinθ cannot be more than 1.
  4. Apr 20, 2009 #3
    thanks! I read the problem incorrectly is mm to meters.
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