  In this article, we discuss the propagation of scalar fields in conformally
transformed spacetimes with either minimal or conformal coupling. The
conformally coupled equation of motion is transformed into a one-dimensional
Schr\"{o}dinger-like equation with an invariant potential under conformal
transformation. In a second stage, we argue that calculations based on
conformal coupling yield the same Hawking temperature as those based on minimal
coupling. Finally, it is conjectured that the quasi normal modes of black holes
are invariant under conformal transformation.
