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Homework Help: Another light question

  1. Jun 19, 2008 #1
    1. The problem statement, all variables and given/known data
    monochromatic light of wavelength 616nm is incident on a narrow slit. On a screen 1.7m away, the distance between the second diffraction minimum and the central maximum is 1.8cm. What is the width of the slit in mm?

    2. Relevant equations

    3. The attempt at a solution
    For the question i use the formula lambda = y x w / L
    where L is the length to screen, y is the distance between the middle of the bright spot and the first dark line and w is the slit width. I rearrange the equation to get w and then just pug in the values and I get w = lambda x L / Y and the answer i get is w = 616E-9 x 1.7 / 0.018 = 5.82E-5m, bbut this answer is incorrect, can someone please help me with whatim doing wrong
  2. jcsd
  3. Jun 20, 2008 #2


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    Staff Emeritus
    Science Advisor
    Gold Member

    The question gives the distance to the second minimum not the first.
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