  We consider scattering exponents arising in small-angle scattering from
power-law polydisperse surface and mass fractals. It is shown that a set of
fractals, whose sizes are distributed according to a power-law, can change its
fractal dimension when the power-law exponent is sufficiently big. As a result,
the scattering exponent corresponding to this dimension appears due to the
spatial correlations between positions of different fractals. For large values
of the momentum transfer, the correlations do not play any role, and the
resulting scattering intensity is given by a sum of intensities of all
composing fractals. The restrictions imposed on the power-law exponents are
found. The obtained results generalize Martin's formulas for the scattering
exponents of the polydisperse fractals.
