Talk:Refractive index
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www.ultra-faster-than-light.com
The above was added by an anonymous user. Hmmm... I wonder who. See http://groups.google.com.au/groups?th=ed639d47fcb6ca32 for some jaded responses to the website. -- Tim Starling
From article:
When light enters a diamond, the high refractive index causes it to suffer multiple total internal reflections, which is the reason for the brilliance of these gemstones.
Removed. The total internal reflection is not special to diamonds, nor is is a natural property of diamonds. The stone must be cuts specially to show it, and the same can be done with other stones (most noticablly with cubic zirconia, and rock crystal). I can't think of a useful way to put this that illuminates (har-har!) anything to do with refractive index.
!! Recommendation: phase velocity should be named v instead of v, which does not differ from greek letter <math>\nu<math> Germendax 09:20, 3 Mar 2004 (UTC)
The problem is, it's standard in publishing and in Wikipedia to use italic letters for variables. The Tex-wiki markup does this when rendering as HTML, for instance. Anyway, the how distinguished v is from ν depends on your browser and which fonts you are using - they are quite clearly distinct on my setup (default IE6), for instance. -- DrBob
Why not use v_p for phase velocity and v_g for group velocity. This seems to be fairly common. Or, use c for phase velocity (reserving c_0 for the vacuum speed of light).
Quoted Indeces
I took the liberty of removing the incomplete table of refractive indices. It was the same as the one in list of indices of refraction, so it's still available. Incidentally, I don't think it's all that useful to quote indices for X-rays. Which wavelength do we pick? Tantalate 16:08, 16 May 2004 (UTC)
- It is standard practice to quote the index at nD20, that is the sodium 'D' doublet is used at 20 C. You will see such values tabulated as nD20. --Askewmind | (Talk) 01:47, 15 Mar 2005 (UTC)
Intro
I'm no physicist, but this seems incorrect to me:
- For a non-magnetic material, the square of the refractive index is the material's dielectric constant ε (sometimes expressed as the relative permittivity εr multiplied by the permittivity of free space, ε0). For a general material it is given by:
- <math> n=\sqrt{\varepsilon\mu}<math>
- where μ is the permeability of free space.
First of all, isn't dielectric constant εr? Second, <math>\sqrt{\varepsilon\mu}<math>, with μ the permeability of free space, can't apply to a "general material"; it takes no account of μr. Should this be <math>\sqrt{\varepsilon_r\mu_r}<math>? Josh Cherry 15:33, 17 Apr 2005 (UTC)