# X-ray diffraction or reflection?

1. Dec 24, 2013

### 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.

2. Dec 24, 2013

### TumblingDice

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.

3. Dec 30, 2013

### sreerajt

does anybody have any other answer????

4. Dec 31, 2013

### M Quack

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/pdf_file/0010/721/chap4.pdf, near page 40.

5. Jan 1, 2014

### TumblingDice

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

6. Jan 2, 2014

### sreerajt

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??

7. Jan 3, 2014

### M Quack

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.

8. Jan 4, 2014

### sreerajt

Okay.. Thank you.....