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Wave optics

  1. Dec 9, 2007 #1
    1. The problem statement, all variables and given/known data
    You want to photograph a circular diffraction pattern whose central maximum has a diameter of 1.0 cm. You have a helium-neon laser (lambda=633 nm) and a 0.12-mm-diameter pinhole.
    How far behind the pinhole should you place the viewing screen?

    2. Relevant equations

    3. The attempt at a solution

    I'm not understanding how to go about doing this/starting this question
  2. jcsd
  3. Dec 9, 2007 #2


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    Half angular width of the central maximum = lambda/d, where d is the slit width.
    And half angle = radius of the central maximum/distance of the screen.
  4. Dec 10, 2007 #3
    so I do 633 nm/1 cm --> of course I will convert to uniform units
    and half angle is 0.5 cm/x

    but how do I use these?
    and should i be using the 1 cm or the .12 mm?
  5. Dec 10, 2007 #4


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    633*x^-9/0.12*10^-3 = 0.5*10^-2/x
    Last edited: Dec 10, 2007
  6. Dec 10, 2007 #5
    so I did that and it's not right. so then I tried using 0.12 x 10^-3 instead of 0.06x 10^3
    and I solved for x, and it's not right.....
  7. Dec 10, 2007 #6


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    x = 0.5*10^-2*0.12*10^-3/633*10^-9 = 0.95m
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