Fig 2X-ray diffractometerDrag to turn θθ 8.0° · 2θ 16.0° · d 3.00 Å · no reflection
Diffracted beam: lit only when nλ = 2d sinθCrystal on a goniometer head, detector on a 2θ armThe crystal turns by θ and the detector arm swings by 2θ. For d = 3.00 Å and λ = 1.5418 Å (example values), the beam reaches the detector near θ = 14.9, 30.9, 50.4°, orders n = 1 to 3.