  Using the 1+3 formulation of stationary spacetimes we show, in the context of
gravoelectromagnetism, that the plane of the polarization of light rays passing
close to a black hole undergoes a rotation. We show that this rotation has the
same integral form as the usual Faraday effect, i.e. it is proportional to the
integral of the component of the gravomagnetic field along the propagation
path. We apply this integral formula to calculate the Faraday rotation induced
by the Kerr and NUT spaces using the quasi-Maxwell form of the vacuum Einstein
equations.
