The Hamiltonian theory of the photon acceleration has been generalized for
the case of electromagnetic wavepackets moving in space and time varying gr
avitational fields. It is shown that due to nearly equal phase velocities o
f the photons and gravitational waves;there appears a significant frequency
shift. Such an efficient mechanism for the photon acceleration can eventua
lly provide an alternative explanation for the observed gamma-ray bursts, F
urthermore, it is also found that in the limiting case of a static gravitat
ional field, the newly derived equations provide a simple and elegant descr
iption of the well-known gravitational redshift and gravitational lens. In
more general terms, the present theory provides a novel coupling mechanism
between the electromagnetic and gravitational waves. (C) 1998 Elsevier Scie
nce B.V.