Questions tagged [phase-velocity]

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Group velocity, phase velocity and signal velocity for axion like particles

In dark matter models of axion-like particles (ALPs), sometimes we get the field $$\phi=2\phi_0\sin(m_\phi c^2 t/\hbar)\cos(k_\phi x)$$ This is like an stationary field with amplitude $\phi_0$ (in m/s ...
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The velocity of a quantum mechanical plane wave of a photon

There is a famous "derivation" or "demonstration" that is often presented in introductory classes in quantum mechanics. I find it deeply unsettling and I feel like key information ...
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Phase difference in Michelson Interferometer

I'm currently taking a quantum mechanics course in university and our professor introduced us to the Michelson Interferometer (or at least what I believe is an apparatus based on it), where a light ...
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What does "non-dispersive" mean in terms of waves and group velocity?

I'm confused about the term wave group velocity: It is usually explained in terms of a superposition of harmonic waves with very closely spaced wave vectors and frequencies. It is then easily shown, ...
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1 vote
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Why the phase velocity of X-rays inside glass is faster than $c$?

For hard X-rays the refraction index of glass becomes slightly $n<1$ which means that the phase velocity (not group velocity) of X-rays inside glass is larger than $c$ the group velocity speed ...
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Can radiative transfer theory be used to calculate an effective index of refraction?

As I understand it, the (real) index of refraction is given by the ratio of speed of a monochromatic light wave in vacuo versus speed in medium. When it comes to the question of propagation of a light ...
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Coupled microstrip waveguide: Why do the even and odd modes have different wave velocities?

Why do the odd and even modes in a coupled microstrip waveguide have different phase velocities? Is this also the case for a coplanar strips waveguide?
1 vote
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How to calculate the phase velocity of a partial standing wave

Partial Standing Waves Partially Reflected Wave A traveling wave encountering an impedance change will be partially reflected and transmitted. It can be represented as the sum of the incident (...
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Why is the velocity of a wave given by $v=\lambda{}f$ different than differentiation?

As obvious from the nature of this question, I am a first-year physics student (with an absent lecturer), and I am having trouble grasping the concept of wave velocity. I've read these answers (1,2) ...
109 views

Confused about the Kelvin wake pattern

What are the $v_{\text{phase}}$ and the $v_{\text{group}}$ in Kelvin wakes? Additionally there are tons of water waves combined to form the kelvin wake. How is it possible for the $v_{\text{group}}$ ...
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Is the observed speed of an infinite set of perfect ocean waves of constant amplitude and frequency independent of an observer's motion?

I am asking this question because it occurred to me that wave propagation has some generally under considered properties regardless and independent of the medium in which the waves are propagating. ...
Why Klein-Gordon and Dirac's waves have a phase velocity of $c$?
From De Broglie’s relations and the energy-momentum dispersion relation one finds: $$v_p=\frac{w}{k}=\frac{E}{p}=\frac{\gamma mc^2}{\gamma mv}=\frac{c^2}{v} \tag{1}$$ Where, $v_p$ is the phase speed ...