  We study the absorption of a massless scalar field by a static black hole.
Using the continuity equation that arises from the Klein-Gordon equation, it is
possible to define a normalized absorption rate $\Gamma(t)$ for the scalar
field as it falls into the black hole. It is found that the absorption mainly
depends upon the characteristics wavelengths involved in the physical system:
the mean wavenumber and the width of the wave packet, but that it is
insensitive to the scalar field's strength. By taking a limiting procedure, we
determine the minimum absorption fraction of the scalar field's mass by the
black hole, which is around 50%.
