1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Bragg condition

  1. Aug 21, 2009 #1
    1. The problem statement, all variables and given/known data

    The unit cell in a cubic crystal is 2.74Å. Determine the Bragg angle for reflections from the planes (200), (212) and (-112). [sorry i dunno how to put a bar on top of the numbers] if the x-ray wavelength used is 1.54Å

    2. Relevant equations
    Given Bragg's condition as 2d sinθ = nλ

    and d = 2π /|G|
    where G = ha* + kb* + lc* according to Laue condition.

    there's also d = a /√(h^2 + k^2 + l^2 )

    where a is the edge length.

    3. The attempt at a solution
    Since d is the distance between planes in atomic lattice, I guess it meant the distance of (200), (212) and (-112) to the origin. So I calculated is by finding the magnitude of G. Then i got confused by the two d equations. Should I use 2π or a to divide with |G| to find the Bragg angle? I thought a is more logical, but the 2π /|G|[/I] is making me confused. What are the difference between them?
    Last edited: Aug 21, 2009
  2. jcsd
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted