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Homework Help: How many bright fringes?

  1. Feb 8, 2017 #1
    1. The problem statement, all variables and given/known data
    At most, how many bright fringes can be formed on either side of the central bright fringe when light of wavelength 644 nm falls on a double slit whose slit separation is 3.64 × 10-6 m?

    2. Relevant equations
    m=dsintheta/lamdba


    3. The attempt at a solution
    m=(3.64x10e-6)(1)/644x10e-9) = 5.65 which is 6 bright fringes right but the system telling me it's wrong?
     
  2. jcsd
  3. Feb 8, 2017 #2

    blue_leaf77

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    What is the width of each slit? Without this information your question cannot be answered.
     
  4. Feb 8, 2017 #3
    That's the full question.
     
  5. Feb 8, 2017 #4

    ehild

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    Can the 6th fringe form?
     
  6. Feb 9, 2017 #5
    I'm not sure so I'm guessing no
     
  7. Feb 9, 2017 #6

    haruspex

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    Last time I checked, 5.65<6.
     
  8. Feb 9, 2017 #7

    ehild

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    What would be sin(θ) at the 6th fringe? Is it possible?
     
  9. Mar 30, 2018 #8
    The brightness fringe should not be rounded from the equation. so yes the answer from the equation is 5.65. Which makes the greatest fringe 5 not 6.
     
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