Radiation force and the classical mechanics of photons and phonons

From simple physical arguments based on adiabatic invariance, energy conservation, and energy quantization the radiation force f due to a reversible or weakly attenuated beam of light, sound, polarons, relativistic electrons, water waves, Seltzer bubbles, bathyspheres, or any other type of propagating energy in any isotropic medium is shown to be given by f = W/c = Eẋ/c where the beam is characterized by its power W, energy/length E, phase velocity c, and energy velocity = group velocity = particle velocity ẋ. Published data is found to be in agreement, although not to the exclusion of all other theoretical alternatives, and further experiments are suggested. Acceptance of this expression for f is shown to imply, in turn, that classical mechanics can be reformulated to embrace any zero− or finite−rest−energy particle. Geometrical optics and acoustics which become special cases are thus extended to the dynamics of classical photons and phonons.