  It was suggested earlier that the gravitational redshift formula can be
invalid when the effect of the backscattering is strong. It is demonstrated
here numerically, for an exemplary electromagnetic pulse that is: i) initially
located very close to the horizon of a Schwarzschild black hole and ii)
strongly backscattered, that a mean frequency does not obey the standard
redshift formula. Redshifts appear to depend on the frequency and there
manifests a backscatter-induced blueshift in the outgoing radiation.
