X-ray diffraction or reflection?

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Discussion Overview

The discussion centers around the terminology and concepts related to x-ray diffraction and reflection, exploring the reasons behind the use of the term "diffraction" despite the occurrence of reflection phenomena. Participants examine the definitions and implications of these terms in the context of x-ray interactions with crystal structures.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants note that x-ray diffraction involves reflection but argue that it is primarily diffraction occurring, as indicated by the patterns generated when x-rays interact with crystal planes.
  • Others explain that reflection is typically associated with surfaces of homogeneous media, while diffraction is related to the interference of wavelets from periodic arrangements, such as crystal lattices.
  • A participant references the Bragg condition, suggesting that the term "Bragg reflection" is commonly used, although they acknowledge that it might be more accurate to refer to it as diffraction.
  • Links to external resources, such as Wikipedia articles on x-ray optics and crystallography, are shared to provide additional context and information.
  • Some participants express confusion about the terminology, questioning how spots in diffraction patterns can be termed reflections when reflection is a distinct physical phenomenon.

Areas of Agreement / Disagreement

Participants express differing views on the terminology and conceptual understanding of x-ray diffraction and reflection. There is no consensus on whether the term "reflection" is appropriate in this context, and the discussion remains unresolved regarding the definitions and implications of these terms.

Contextual Notes

The discussion highlights the complexity of terminology in physics, particularly in the context of x-ray interactions, and the potential for confusion arising from overlapping concepts of reflection and diffraction.

sreerajt
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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.
 
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sreerajt said:
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.
 
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does anybody have any other answer?
 
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.
 
sreerajt said:
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.
 
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TumblingDice said:
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 :wink:) 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??
 
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.
 
Okay.. Thank you...
 

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