Talk:Brillouin scattering

There should be a classical description of Brillouin scattering, e.g. soundwaves thought of a pressure as a function of time -> index of refraction fluctuation with pressure -> diffraction of light —Preceding unsigned comment added by 99.244.83.206 (talk) 04:33, 30 September 2009 (UTC)

Brillouin vs. Raman
Why to compare Brillouin and Raman? Brillouin can be described as a macroscopic, classical phenomenon, as a diffraction of the electromagnetic wave on the grid created by the periodic variation of density/polarity, and hence of dielectric constant, generated by the acoustic wave, without speaking of photons and phonons. Raman, instead, is definitely microscopic: just one molecule. And, it is true that they are both anelastic. But, the anelasticity of Brillouin is not so crucial: a small Doppler shift and a small energy/momentum change diluted over many molecules. For Raman, the anelasticity is the phenomenon. Raman is strongly dependent on the detailed structure of the molecules involved, Brilloun (al least B. from phonons), not so much. Perhaps, Brillouin is more comparable to Rayleigh, the difference being that the refraction index fluctuations are correlated and periodic in Brillouin, random and incoherent in Rayleigh. --GianniG46 (talk) 09:37, 3 June 2010 (UTC)

Merging with 'Scattering'
I do not agree with the proposed merge. Scattering is everywhere, from sky to almost every object we see, so it is a much wider and less "specialistic" phenomenon than Brillouin. Rather I proposed to merge here a couple of sections of the article "Light scattering" containing a discussion of phohons and Brillouin which I believe too detailed for that article.--GianniG46 (talk) 07:18, 25 June 2010 (UTC)


 * I will not oppose the merging of the sections from the article Light scattering entitled Elastic waves and Brillouin scattering into the article on Brillouin scattering -- as long as they are transferred in their entirety. I feel that they would strengthen that article significantly, and may be easily referenced in the article on Light scattering in general. logger9 (talk) 16:58, 25 June 2010 (UTC)


 * I would propose that these 2 sections from the article on Light scattering be inserted in their entirety into the article on Brillouin scattering immediately following the section in that article currently entitled Mechanism. logger9 (talk) 18:25, 25 June 2010 (UTC)

PRAISE: What makes this a successful teaching article?
This is a great little article. Too bad it will never be recognized as a "Featured Article" because of its modest size. Yet it has great teaching value and didactic excellence. A reader can learn from it.

We will never see comments like these that readers took the trouble to make for another article: 1. "... the rest of us have no idea what you're talking about." 2. "Huh^2. I'm a math/s graduate and I haven't the faintest clue what this article is about." 3. "I have an undergrad degree in mathematics and this is all Greek to me. . . . The article is completely inaccessible to the layperson." 4. " I have degrees in both math and physics and have no idea what this article is talking about." 5. " I understand, to some reasonable degree, both of einsteins theories, i got an 800 on my math sat, and i have absolutely no idea what this article is about."

The Brillouin Scattering article succeeds. What can we learn from it? Why is this article so useful?

IMHO, two characteristics give this article excellence in helping others learn:

1. COMPARE AND CONTRAST

Just because we have hyperlinks to other articles, we should not shrink from making comparisons to -- and drawing attention to differences from -- other related concepts. It is permissible to clarify for readers and for ourselves the similarities and differences with other items -- other physical effects, other political philosophies, a competing conceptual construct -- even if those items have their own articles. Sending a reader on a page bounce pales in comparison to the teaching that editors can achieve for the community through their clarification of competing concepts.

2. MULTIPLE WAYS OF DEFINING/LOOKING AT IT

For teaching readers, it is OK to present multiple conceptualizations of an effect or named "thing", rather than to insist on crafting the most "correct" one. For example, the scattering of light by matter is caused by inhomogeneities, and these may be viewed as subwavelength particles (dust makes the sky blue), or individual molecules (that absorb or impart energy), or variations seen as density differences or refractive index differences, whose interactions are either quantized or not, are electromagnetic or not (phonons).

There is a third issue: how an article opens.

3. THE LEAST OBJECTIONABLE DEFINITION

A definition is an obvious start, right? No so fast.

This brief Wikipedia article on Brillouin Scattering has illuminated how light is scattered by matter, and, in doing so, has shed light on Brillouin, Raman and Raleigh scattering. This is not the same as struggling to craft the least objectionable definition of each one. Such "least objectionable definitions" must often be general;  to be general, specifics must be omitted; without specifics, the reader gets less information.

It may sometimes be necessary to begin with a "loose", more basic definition, and then refine it, then develop the exposition. There will be exceptions to a basic definition which invalidate it, which make it wrong in some cases. We can deal with this, don't worry. Editors who struggle to achieve a definition that handles all objections -- the least objectionable definition -- deprive themselves of a natural way to develop the entire article, to carry the article from the broad to the specific. And, the Least Objectionable Definition -- to those who know what they are talking about -- may become useless to those who have come here to learn.

This article helped me, and I thank all of you. :-) Jerry-va (talk) 13:06, 21 October 2012 (UTC)