  We consider the scattering of lightlike matter in the presence of a heavy
scalar object (such as the Sun or a Schwarzschild black hole). By treating
general relativity as an effective field theory we directly compute the
nonanalytic components of the one-loop gravitational amplitude for the
scattering of massless scalars or photons from an external massive scalar
field. These results allow a semiclassical computation of the bending angle for
light rays grazing the Sun, including long-range $\hbar$ contributions. We
discuss implications of this computation, in particular the violation of some
classical formulations of the equivalence principle.
