1. The problem statement, all variables and given/known data A certain crystal has a set of planes 0.33 nm apart. A beam of neutrons strikes the crystal at normal incidence and the first maximum of the diffraction pattern occurs at ∅= 38°. What is the de Broglie wavelength of the neutrons? 2. Relevant equations nλ = Dsin∅ where D = d / sinα and α = ∅/2 3. The attempt at a solution First, I found D: D = .33nm / (sin(38/2)) = 1.014 This D corresponds to the spacing of the atoms and the d given in the problem statement corresponds to the spacing of the planes in the crystal. I assume n = 1. Then λ = 1.014 nm * sin(38) = .624 The answer .59. What am I doing wrong? The only thing that I can think of that I might be doing wrong is my n is incorrect.