  We study the evolution of scalar perturbations in the radiation-dominated era
of Randall-Sundrum braneworld cosmology by numerically solving the coupled bulk
and brane master wave equations. We find that density perturbations with
wavelengths less than a critical value (set by the bulk curvature length) are
amplified during horizon re-entry. Conversely, we explicitly confirm from
simulations that the spectrum is identical to GR on large scales. Although this
magnification is not relevant for the cosmic microwave background or
measurements of large scale structure, it may have some bearing on the
formation of primordial black holes in Randall-Sundrum models.
