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 Δr=2dcosθm=mλ 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.