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Homework Help: The angle of the first order diffraction

  1. Apr 29, 2012 #1
    1. The problem statement, all variables and given/known data

    What is the angle of the first order diffraction, m=1, when X-rays diffract from a crystal in which a spacing between atomic planes is 0,175nm? The 2nd diffraction, m=2, occurs at 45o.

    2. Relevant equations
    m+1/m = cos45/cosθm , because when the m increases the θm decreases.

    3. The attempt at a solution
    m+1/m = cos45/cosθ1
    θ1 = 69o.

    What do you think? Just asking because I am not 100% sure.
  2. jcsd
  3. Apr 29, 2012 #2
    Last time I checked, Bragg's law was m lambda = 2 d sin(theta)...

    Higher order reflections always occur at larger Bragg angles.
  4. Apr 29, 2012 #3
    I my case it is cosθm. Yep, I think this should be the right answer because the angle is bigger than 45o.
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