- #1
Yu-Ting
In the "Introduction to Solid State Physics" by C. Kittel, there is a long wavelength limit in chapter 4 -Phonons I.
When Ka << 1 we can expand cos Ka ≡ 1 - ½ (Ka)2
the dispersion relation will become ω2 = (C/M) K2 a2
Does anyone know what frequencies can allow this long wavelength limit to hold?
When Ka << 1 we can expand cos Ka ≡ 1 - ½ (Ka)2
the dispersion relation will become ω2 = (C/M) K2 a2
Does anyone know what frequencies can allow this long wavelength limit to hold?