Volume 17: Pages 159-165, 2004

The Two Velocities of Classical Waves

J. P. Wesley

Weiherdammstrasse 24, 78176 Blumberg, Germany

Classical waves in a medium, valid for light and for sound, involve two velocities, the phase velocity c′ and the energy velocity c, which in general are different both in direction as well as in magnitude. Doppler effects for a moving source and observer and for a wind are derived. The out‐and‐back phase velocity of a wave in a wind is proved to be isotropic according to classical wave theory, which explains the Michelson‐Morley null result as simply a classical Doppler effect. Feist has recently experimentally demonstrated the isotropy of the out‐and‐back phase velocity of sound in a wind, thereby confirming classical wave theory and duplicating for sound the Michelson‐Morley null result for light.

Keywords: classical waves, light, sound, phase velocity, energy velocity, Michelson‐Morley, Feist's results

Received: September 30, 2003; Published online: December 15, 2008