X-ray crystallography

[darkheavens]

Hi guys, do any of you know why there are varying peak heights in graphs such as the one below?
If the intensity only changes if you move the x-ray source towards/away from the object, then shouldn't the peak heights be the same given that the distance has not changed?

http://www.gly.uga.edu/Schroeder/geol6550/Antigorite_XRD.jpg

[Cthulhu]

X-ray diffraction in crystals also depends on the angle of the X-ray. Bragg's Law or something. It's been about 6 months since I did the experiment.

[/0]

If what you're doing is a Bragg's law experiment, then there should only be constructive interference (and hence an intensity peak) when

, where is the lattice separation.

If you check hyperphysics they probably have a good explanation