Energetic and optical consequences of light distortion inside an expandingisotropic sphere

The propagation of light inside a moving inhomogeneous medium is modified b y two distortion phenomena. The phase function of light changes as a result of both the spatial variation of the refractive index and the motion of ma tter. We deal with the expanding or collapsing motions of a dielectric and study propagation of light in such a medium within the geometrical optics a pproximation. A correction of the famous Clausius principle and Bouguer's l aw is given to take into account the distortion of light and to correct the classic form of the radiative-transfer equation. We prove that the express ion of a new energetic invariant is a direct consequence of local dilatatio ns of space-time that are due to both the Doppler shift that arises from th e problem of unsteady optics and the phase distortion phenomena assigned to the velocity field. (C) 2001 Optical Society of America.