We study magneto-optically induced rotation and ellipticity of resonan
t linearly polarized light incident on an atomic vapour. We allow for
an arbitrary strength and direction of the magnetic field, and arbitra
ry degree of saturation. For magneto-optical rotation, the result is t
he sum of an absorptive and a dispersive contribution, which represent
a generalized Voigt and Faraday effect respectively. These terms are
not independent, since both depend on the steady-state density matrix
of the atoms in the field. A similar separation is found for the induc
ed ellipticity, with dispersive and absorptive terms interchanged. The
rotation angle is numerically evaluated for a simple atomic transitio
n. The symmetry properties of the dipole polarization are discussed. (
C) 1998 Elsevier Science B.V. All rights reserved.