Dispersion relation Definition and 65 Threads

  1. D

    The dispersion relation of waves between two layers of varying density

    Homework Statement Show that c^2 = g/k*(rho1 - rho2)/ (rho1 + rho2) where rho1 and rho 2 are the different densities, k is the constant from solving the PDE (separation of variables). Homework Equations Use the fact that phi(1) --> 0 as y --> neg. infinity and phi(2) --> 0 as y -->...
  2. S

    Find dispersion relation using periodicity

    Ok so here's another problem that i just completely don't understand at all. Thanks for your help. A linear chain consists of 2N equally spaced identical particles with mass m and speration a, coupled by springs with alternating constands k1 and k2. Use the periodicity of the system to find...
  3. E

    Experimental dispersion relation of phonons

    Hi guys, I don't understand how one would exactly determine a dispersion relation of phonons experimentally. There are two equations, one for momentum and one for energy conservation: \vec{k} - \vec{k^{'}} = \vec{G} + \vec{K} \omega - \omega ^{'} = \omega(K) where...
  4. S

    Dispersion Relation of a De Broglie Wave

    Homework Statement Use the dispersion relation to find the group velocity v_group and phase velocity v_phase. Homework Equations omega(k) = [(hbar)k^2]/2m The Attempt at a Solution v_group = domega(k)/dk = [hbar]k/m = h/m lambda = p/m = v This isn't right. v_phase = omega...
  5. Y

    3d rossby wave frequency dispersion relation

    Homework Statement Consider the linearized, quasi-geostrophic vorticity equation on the beta-plane, with a mean background flow umean , which allows for vertical structure and propagation of Rossby waves: (d/dt+umean*d/dx)=(nabla2 ψ+(f02/N2)*(d2 ψ/dz2)+bv where ψ is the horizontal...
  6. Y

    Dispersion Relation: What is it for Photons?

    What is the dispersion relation in photons? "(Frequency momentum or etc)
  7. L

    Dispersion Relation and wavelength

    I've been working on problems trying to find the dispersion relation of monatomic and diatomic chains. I'm able to find the dispersion relation, but I don't really understand what it is. I'm pretty sure that it's the relation of the frequency to the wave vector. I'm working through Kittel's...
  8. X

    One dimensional lattice dispersion relation

    I'm doing an experiment, in which I have a one dimensional lattice held up by strings. That is I have a series of n masses each of mass M each connected to each other by springs with spring constant C and unstretched length a. Each mass is suspended from the ceiling by a string of length L. I'm...
  9. E

    Calculating Group Velocity of Schrodinger Waves: Dispersion Relation

    The group velocity of traveling wave is defined as v_g =\partial \omega/\partial k. I am confused about how to actually calculate this. For instance, in the Schrodinger equation, we find that plane waves solve the equation provided that \omega = k^2 \hbar/2m Does this mean that the group...
  10. H

    Dispersion Relation KdV equation

    Hi all. I have some questions about the dispersion relation in the study of waves. First of all, why do we always assume a plane wave solution when we want to obtain a dispersion relation? Second, is "assuming a plane wave solution" a general way to obtian all dispersion relations? for both...
  11. A

    Dispersion relation diagrams, phonons

    In dispersion relation diagrams, where omega is plotted against k, omega is sometimes nonzero at k=0. How is this possible? I thought a wave had to have a nonzero wavenumber :confused:
  12. B

    MATLAB Dispersion relation with Matlab

    I'm studying the phenemenon of band gaps in a experiment, however the stop bands are proving hard to define using just a transmission spectrum dervived from the fft alogrithm. I've heard that it may be possible to define the band region by plotting the dispersion relation of sound waves the...
  13. G

    Dispersion relation for light in vaccuum

    Hello, I was wondering if someone more knowledgeable in loop-quantum gravity or string theory could discuss a bit about the following topic for me: If there is a lower size limit (or length itself is quantized), does this (or can this) mean that there would be a dispersion relation for light...
  14. Q

    Dispersion Relations: Confusing Me & What Information is Gained?

    Dispersion relations have the tendency to confuse me. In general, I know what dispersion is, but trying to apply it to crystals, I just "can't see the forest among all those trees". :rolleyes: In phonon dispersion, acoustical and optical phonons have quite a different dispersion behaviour...
  15. J

    Explaining Dispersion Relation for Free Electron - Jayse

    Hi, please could someone explain the term dispersion relation to me, particularly for the case of a free electron? Thanks Jayse
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