Cubic unit cell diffraction

Now we will look at a larger crystal - in this case with 20 Angstrom cell axes.

Rotate the crystal 1° counterclockwise. A number of spots should appear on the top half of the detector. By looking at the view edge on, you should be able to see that some of these come from the (1kl) layer and some from the (2kl) layer. Continue to rotate the crystal until the (010) spot appears near the centre of the detector. What is θ for this reflection?

Clear the detector and continue to rotate the crystal until you see lunes emerging. How far can you rotate the crystal before the first overlapping spots appear? In a real experiment we would need to start collecting a new image before this point. The larger the unit cell, the smaller the angle through which we can rotate the crystal while collecting a single image.

Rotate the crystal to θ=20° and clear the detector. Position the camera for an edge-on view, and rotate the crystal counter clockwise until the first (1kl) spot appears. What is θ?