  The redshift of light is calculated for an anisotropic cosmological
spacetime. Two different approaches are considered. In the first one,
electromagnetic waves are modeled using the geometrical optics
(high--frequency) approximation. This approach considers light rays following
null geodesics, being equivalent to the motion followed by pointlike spinless
massless particles. It is shown that the redshift for this case depends, in
general, on the direction of propagation, and is dispersive (wavelength
dependent) for light emitted from different points of an extended object. In
the second approach electromagnetic waves are studied using the exact form of
Maxwell equations, finding that redshift has dependence on the direction of
propagation as well as on the wave polarization. The electromagnetic waves are
dispersive and depend on the anisotropic temporal evolution. In this last case,
redshifts may become dispersive depending on the relative direction between the
light ray propagation vector and the anisotropy axes. The relation of these
results with a possible violation of the Equivalence Principle are discussed.
In general, both results are set in the context of recent astrophysical
redshift observations for anisotropic cosmologies, and new ways of determining
redshifts are suggested.
