Note on Group Velocity and Energy Propagation

A general proof is given for the equality between group velocity and energy velocity for linear wave propagation in a homogeneous medium with arbitrary spatial and temporal dispersion. In the series of physics \Questions " in the American Journal of Physics, K. M. Awati and T. Howes ask for a general proof of the fact that in linear dispersive wave propagation, energy propagates at the group velocity [1]. Several answers to this question have appeared recently [2], but a general proof has not been provided by any of them. For a stable and nondissipative [3] medium, such a general proof is indeed available from classical, continuum electrodynamics of media [4]. It can be readily argued that this type of proof 1 can be carried out for any other (than electrodynamic) description of a stable, nondissipative, linear (or, more generally, linearized dynamics of a) medium. In an electrodynamic formulation, one chooses to eliminate the \mechanical&quot

Microwave Electronics

Contains a report on a research project.Lincoln Laboratory (Purchase Order DDL-B222)United States Air Force (Contract AF19(604)-5200)United States Navy, Office of Naval Research (Nonr-1841(49)

Spontaneous Radiofrequency Emission from Hot-Electron Plasmas

Contains research objectives.United States Atomic Energy Commission under Contract AT(30-1)-358

Network Synthesis

Contains a report on a research project

Spontaneous Radiofrequency Emission from Hot-Electron Plasmas

Contains report on one research project.U. S. Atomic Energy Commission (Contract AT (30-1)-3581

Microwave Electronics

Contains reports on one research project

Microwave Electronics

Contains reports on three research projects

Microwave Electronics

Contains reports on three research projects.United States Department of the NavyLincoln Laboratory (Purchase Order DDL-B222)United States Department of the ArmyOffice of Naval Research (Contract Nonr-1841(49)United States Department of the Air Force (Contract AF19(122)-458

Microwave Electronics

Contains a report on a research project.United States ArmyUnited States Navy, Office of Naval Research (Contract Nonr-1841(49))Lincoln Laboratory (Purchase Order DDL B-00368)United States Air Force (Contract AF19(604)-7400)United States Nav

Relativistic Beams

Contains reports on two research projects.Joint Services Electronics Programs (U. S. Army, U.S. Navy, and U. S. Air Force) under Contract DAAB07-71-C-030