1. The problem statement, all variables and given/known data X-rays of wavelength λ are incident on a cubic crystal with spacing d as shown in the figure. The incident angle is fixed at θi degrees. A detector is rotated from perpendicular to the 100 plane (90 degrees (grazing)) until the first maximum is detected at θs degrees due to interference from the 100 plane. What is the lattice spacing, d, of the cubic crystal? 2. Relevant equations Bragg's Law : mλ=2dsinθ 3. The attempt at a solution Known: m=1, λ The angle to be used for Bragg's Law is not the incident/reflected angle because θs does not equal θi. So I figured out the angle between the incoming and reflected ray (180-θs-θi=θsplit) and that would not be the angle we are looking for either. So i divided that θsplit by 2, and subtracted it from 90. To find what I thought was the correct angle but apparently not. If this is not the angle, what is and how do i get to it? Is m≠1 despite the problem stating "first order maximum"? is my θs not the correct angle? Thank you in advance. also sorry about the images, they work better if you drag them into a new tab.