Bragg diffraction - How to make sense of it ?

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    Bragg Diffraction
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Discussion Overview

The discussion centers on understanding Bragg diffraction, particularly the challenges of explaining it without oversimplified concepts like the reflection of X-rays by parallel planes. Participants express confusion over common explanations and seek a more intuitive grasp of the physical mechanisms involved.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions the adequacy of standard explanations of Bragg diffraction, suggesting they often rely on oversimplified notions.
  • Another participant proposes starting with the Laue equations or the Bloch theorem to derive the Bragg equation, indicating a preference for mathematical formalism.
  • A different participant expresses a desire for explanations that do not depend on mathematical formalism, seeking a general discussion on the physical mechanisms instead.
  • Several participants recommend various academic resources, including dissertations and articles by P. P. Ewald, that provide insights into diffraction patterns and crystal theory without excessive mathematics.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best approach to explain Bragg diffraction. Some advocate for mathematical derivations, while others prefer more conceptual discussions. The discussion remains unresolved regarding the most effective explanatory framework.

Contextual Notes

Participants express varying levels of comfort with mathematical formalism, indicating a potential limitation in communication about the topic. The discussion also highlights the complexity of conveying physical mechanisms behind diffraction without oversimplification.

svrphy
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Bragg diffraction - How to make sense of it ??

Is there a way to make sense of Diffraction of X Rays without taking recourse to oversimplified concepts like "Reflection of X Rays by parallel planes" which is generally the explanation in most basic physics books. It's been a couple years since I first studied it and i continue to get confused by assertions like reflecting of Photons by atoms. Online sources are also full of it :

http://www-outreach.phy.cam.ac.uk/camphy/xraydiffraction/xraydiffraction7_1.htm
OR
http://chemwiki.ucdavis.edu/Analytical_Chemistry/Instrumental_Analysis/Diffraction/Bragg's_Law
 
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You can start with the Laue equations, which are derived from interference principles used in gratings, and derive the Bragg equation from them: http://www.phys.utk.edu/courses/Fall%202009/physics671/chapter1c.pdf

Or you can start with the fully quantum mechanical Bloch theorem and derive the Bragg equation:
http://www.uni-tuebingen.de/meso/ssscript/blochelectrons.pdf

But the Bragg equation is very simple, and very accurate, so I have used it extensively in my electron diffraction work.
 
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I get that. But, is there a way to explain things without relying on mathematical formalism. I mean a general discussion on the physical mechanism.
 
Read chapter two of this dissertation: http://hdl.handle.net/2027.42/63758

It starts with crystal theory, atomic scattering, and elastic scattering from crystals ... in short, a derivation of diffraction patterns starting from scratch.
 
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M Quack said:
This article by P. P. Ewald, one of the founding fathers of x-ray diffraction, give an excellent overview without excessive math.

http://rmp.aps.org/abstract/RMP/v37/i1/p46_1

Thanks for the link. If you have access, could you pls give me the pdf ?
 

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