Klaynos Posted June 2, 2005 Posted June 2, 2005 Just a quick question came up today in some revision had a quick google and found a couple of things but was wondering if anyone here could give me some... Examples of anomalous dispersion, when said in relation to phase and group velocities of wavlettes and wave packets...
Johnny5 Posted June 2, 2005 Posted June 2, 2005 Just a quick question came up today in some revision had a quick google and found a couple of things but was wondering if anyone here could give me some... Examples of anomalous dispersion' date=' when said in relation to phase and group velocities of wavlettes and wave packets...[/quote'] Exactly what are you asking?
Klaynos Posted June 2, 2005 Author Posted June 2, 2005 Just for physical examples of anomalous dispersion...
Johnny5 Posted June 2, 2005 Posted June 2, 2005 Just for physical examples of anomalous dispersion... I think X-ray diffraction for one. Here is wikipedia's article on dispersion. I haven't even read it, but I know what dispersion is. Look at how the prism separates light into frequency bands. A while ago, i studed rainbows, and read all about this. The idea runs like this... the index of refraction n, varies with w, and the speed of light decreases upon entering a material. [math] v_{phase} = \frac{c}{n} [/math] Since the speed of light in matter v, must be less than the speed of light in vacuum c, n has to be greater than 1. Now, there is a way to understand why a rainbow does what it does, and it is the same answer for why a glass prism does it.
Klaynos Posted June 2, 2005 Author Posted June 2, 2005 Thanks. That would be normal dispersion, there are 3 types: Normal: when vg < vp None: when vg = vp Anomalous: when vg > vp It is this third for which I have no examples, and was searching for some, wikipedia appears to be little help...
Johnny5 Posted June 2, 2005 Posted June 2, 2005 Thanks. That would be normal dispersion' date=' there are 3 types: Normal: when v[sub']g[/sub] < vp None: when vg = vp Anomalous: when vg > vp It is this third for which I have no examples, and was searching for some, wikipedia appears to be little help... Right here is the formula I was going for... [math] D = -\frac{\lambda }{c} \frac{d^2n}{d\lambda^2} [/math] If D is greater than zero, then the medium exhibits anamalous dispersion. Now, as for examples, look for experiments in crystallography. There are probably some superconducting crystals which exhibit it. Let me see if i can find something. Here is something that might interest you, i dont know. Anamalous dispersion of optical phonons in high temp superconductors
swansont Posted June 3, 2005 Posted June 3, 2005 Just a quick question came up today in some revision had a quick google and found a couple of things but was wondering if anyone here could give me some... Examples of anomalous dispersion' date=' when said in relation to phase and group velocities of wavlettes and wave packets...[/quote'] You can Google on the phrase and find examples. One that comes up a lot is the light pulse that seemingly exits before it enters a gas cell. More here
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