Using the Einstein solid to model a solid gets the specific heat wrong at low T. One reason is because of the near degeneracy of the electrons, as we've discussed. That is, in the Einstein solid we treated each oscillator as in independent entity, not connected to the neighboring oscillators.
High frequency means small wavelength.
With light, the wavelengths can get as small as they want to, as far as we can tell. But with a phonon, or sound wave, the wavelength can't get any smaller than twice the lattice spacing. If so, describe briefly. Back to the PHYS 317 home page.