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Vacuum polarization in QED in a background gravitational field induces interactions which {\it effectively}
modify the classical picture of light rays, as the null geodesics of spacetime. These interactions violate
the strong equivalence principle and affect the propagation of light leading to superluminal photon
velocities. Taking into account the QED vacuum polarization, we study the propagation of a bundle of ray
in a background gravitational field. To do so we study the perturbative deformation of Raychaudhuri
equation through the influence of vacuum polarization on photon propagation. We
analyze the contribution of the above interactions to the optical scalars namely, shear, vorticity and
expansion using the Newman-Penrose formalism. Finally the application of the effective Raychaudhuri
equation in the context of singularity theorems is discussed.
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