Retrieving "Long Wavelength" from the archives

Cross-reference notes under review

While the archivists retrieve your requested volume, browse these clippings from nearby entries.

1. Phonon

   Linked via "long-wavelength"

   The dispersion curves for a lattice containing $N$ atoms in the primitive unit cell exhibit $3N$ branches in total, $3N-3$ of which are acoustic, and 3 (or 2, in the case of a linear chain) are optical.
   Acoustic Phonons: These modes correspond to long-wavelength vibrations where adjacent atoms in the lattice move essentially in phase. At long wavelengths ($\mathbf{q} \to 0$), the frequency $\omega$ tends to zero. The three acoustic…

2. Rayleigh Jeans Law

   Linked via "long-wavelength"

   The Rayleigh-Jeans Law is a formula derived from classical electrodynamics and statistical mechanics that attempts to describe the spectral radiance of electromagnetic radiation emitted by a black body in thermal equilibrium at a specific temperature, $T$. Developed independently by Lord Rayleigh and Sir James Jeans in the early 20th century, the law provides an accurate description of t…