  We discuss the method of calculating the reflection coefficient using complex
trajectory WKB (CWKB) approximation. This enables us to give an interpretation
of non-reflecting nature of the potential under certain conditions and clarify
some points, reported incorrectly elsewhere [vs:ejp] for the potential
$U(x)=-U_0cosh^2(x/a)$. We show that the repeated reflectios between the
turning points are essential, which most authors overlooked, in obtaining the
non-reflecting c ondition. We find that the considered repeated reflection
paths are in conformity with Bogolubov transformation technique. We discuss the
implications of the results when applied to the particle production scenario,
considering $x$ as a time variable and also stress the cosmological
implications of the result with reference to radiation domonated and de Sitter
spacetime.
