  We reconsider the long-range effects of the scattering of massless scalars
and photons from a massive scalar object in quantum gravity. At the one-loop
level, the relevant quantum mechanical corrections could be sorted into the
graviton double-cut contributions, massless-scalar double-cut contributions and
photon double-cut contributions. In arXiv:1410.7590 and 1609.07477 N.E.J.
Bjerrum-Bohr et al. have considered explicitly the implications of the graviton
double-cut contributions on the gravitational bending of light and some
classical formulations of the equivalence principle, using the modern
double-copy constructions and on-shell unitarity techniques. In this article,
instead we consider all three contributions and redo the analysis using the
traditional Feynman diagrammatic approach. Our results on the graviton
double-cut contributions agree with the aforementioned references, which acts
as a nontrivial check of previous computations. Furthermore, it turns out that
the massless-scalar double-cut contributions and the photon double-cut
contributions do leave non-vanishing quantum effects on the scattering
amplitudes and the gravitational bending of light. Yet, we find that the
general structure of the gravitational amplitudes and the quantum discrepancy
of the equivalence principle suggested in the aforementioned references remain
intact.
