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Homework Help: Light Waves Interference

  1. Aug 16, 2010 #1
    1. The problem statement, all variables and given/known data

    A laser beam ( λ = 694 nm) is incident on two slits 0.100 mm apart. Approximately how far apart (in m) will the bright interference fringes be on the screen 5.00 m from the double slits?

    2. Relevant equations

    [tex]y=L\left( \frac{m \lambda}{d} \right)[/tex]

    3. The attempt at a solution

    [tex]y_{m+1}-y_m = L \left(\frac{(m+1)\lambda}{d} \right) - L \left( \frac{m \lambda}{d}\right)[/tex]

    [tex]= L\frac{\lambda}{d}= 5 \left( \frac{694}{1 \times 10^{-4} m} \right)[/tex]


    So I got the distance between adjacent fringes to be 34700000 which is a very huge number. But the right answer must be 3.47 × 10–2. Any help is appreciated.
  2. jcsd
  3. Aug 16, 2010 #2

    Doc Al

    User Avatar

    Staff: Mentor

    For one thing, the wavelength is 694 nm, not 694 m. (nm = nanometer)
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