# X-ray diffraction or reflection?

by sreerajt
Tags: diffraction, reflection, xray
 P: 28 In x-ray diffraction , even though its reflection is happening , we call this as x ray diffraction. why is it so?? i don't know whether it has been discussed previously here.
PF Gold
P: 207
 Quote by sreerajt In x-ray diffraction , even though its reflection is happening , we call this as x ray diffraction. why is it so?? i don't know whether it has been discussed previously here.
Actually its diffraction that's happening. The terminology 'reflections' applies to the spots/patterns generated when x-rays diffract through a set of evenly spaced planes in a crystal. It's the mathematics of the monochromatic frequency of the x-rays and the angle of diffraction as the crystal is rotated. Diffraction patterns of spots/reflections are generated when the resulting wave patterns coincide and support each other.
 P: 28 does anybody have any other answer????
P: 640

## X-ray diffraction or reflection?

Reflection and diffraction are really two different aspects of the same thing. The term reflection is used mostly for what happens at the surface of a homogenous medium. This does occur for x-rays, but only at very small angles, because the index of refractions is very very close to 1. Nevertheless the effect is used for things like space-based x-ray telescopes, focusing and harmonic rejection of synchrotron radiation, etc.

http://en.wikipedia.org/wiki/X-ray_optics#Reflection

Diffraction relies on the (constructive) interference of wavelets scattered from a period arrangement of objects. For x-rays that can be a crystal lattice, an artificial multilayer, a Fresnel lens structure, etc. Diffraction does not necessarily happen at a surface. In fact, Max von Laue and coworkers first discovered x-ray diffraction in a transmission geometry.

http://www.iucr.org/__data/assets/pd.../721/chap4.pdf, near page 40.
PF Gold
P: 207
 Quote by sreerajt does anybody have any other answer????
M Quack added good info and links for reflection and diffraction.

Here's another wiki link directly to X-ray Crystallography:
http://en.wikipedia.org/wiki/X-ray_crystallography

The link has some more good stuff that directly addresses your question regarding, "why":
 In an X-ray diffraction measurement, a crystal is mounted on a goniometer and gradually rotated while being bombarded with X-rays, producing a diffraction pattern of regularly spaced spots known as reflections.
P: 28
 Quote by TumblingDice M Quack added good info and links for reflection and diffraction. Here's another wiki link directly to X-ray Crystallography: http://en.wikipedia.org/wiki/X-ray_crystallography The link has some more good stuff that directly addresses your question regarding, "why":
You (actually Wikipedia ) are telling is that reflection ".... producing a diffraction pattern of regularly spaced spots known as reflections". But reflection is a physical phenomenon, so how cold you term spots as reflection??
 P: 640 That is just nomenclature. At the Bragg condition the crystal "reflects" (should be diffracts!) x-rays, that's why it is known as Bragg reflection. This is the term that everybody uses, and I do not know of any better term. Get used to it.
 P: 28 Okay.. Thank you.....

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