  In this work, three different particle sizes: the static radius $R_{s}$,
hydrodynamic radius $R_{h}$ and apparent hydrodynamic radius $ R_{h,app}$
obtained using the light scattering technique, are investigated for dilute
poly-disperse homogenous spherical particles with a simple assumption that the
hydrodynamic radius is in proportion to the static radius, when the
Rayleigh-Gans-Debye approximation is valid. The results show that the expected
values of the normalized time auto-correlation function of the scattered light
intensity $g^{(2)}(\tau) $ calculated based on the static particle size
information are consistent with the experimental data. The volume phase
transition is thus investigated using the equilibrium swelling ratios of static
radii and apparent hydrodynamic radii respectively. The changes of the static
particle size information and apparent hydrodynamic radius as a function of
temperature $T$ show the effects of the volume phase transition on optical
properties and the total influences of the volume phase transition on the
optical, hydrodynamic characteristics and size distribution of particles,
respectively. The effects of cross-linker on the volume phase transition are
also discussed.
