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Results tagged with phase-velocity
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user 1325
1
vote
Why doesn't anomalous dispersion allow faster-than-light propagation?
Re your question 2: this is how I like to think about it.
If you have an infinitely long steady light beam it cannot transmit any information, so it doesn't really have a speed. The wave has a phase …
- 363k
2
votes
Why is the phase velocity used in the definition of the refractive index?
Refraction can be described by the Huygen's-Fresnel principle just like diffraction. In this interpretation it is an interference phenomenon with every point on the wave front acting as a source, and …
- 363k
6
votes
Accepted
Phase velocity greater then the speed of light?
The simple answer is that the wave packet travels at the group velocity not the phase velocity, and the group velocity is always less than or equal to $c$.
You might argue that you aren't using a wav …
- 363k
7
votes
$\lambda=\frac{2h}{p}$ instead of $\lambda=\frac{h}{p}$?
The energy $E$ in this case is the total energy i.e. the kinetic energy plus the rest mass energy. For a photon there is no contribution from the rest mass because the rest mass is zero, but for a mas …
- 363k
2
votes
Accepted
Wavefronts and phase velocity faster than $c$
Yes, $v_y$ can be greater than $c$, and in fact it could be as large as you want if the make the angle small enough. However nothing, i.e. no signal, is being transmitted at that velocity so it doesn' …
- 363k
15
votes
Accepted
Seeming violation-wave travelling faster than speed of light
What you have calculated is the phase velocity, $v_p$, of the de Broglie wave associated with the particle. The phase velocity can be greater than $c$, and indeed it is always greater than $c$.
The v …
- 363k