  The results obtained using my computing program are consistent with the
values obtained twenty years ago. It also makes me believe that how to obtain
particle size information using the Light Scattering technique needs to be
reconsidered.
  Static Light Scattering (SLS) and Dynamic Light Scattering (DLS) are very
important techniques to study the characteristics of nano-particles in
dispersion. The data of SLS is determined by the optical characteristic and the
measured values of DLS are determined by optical and hydrodynamic
characteristics of different size nano-particles in dispersion. Then
considering the optical characteristic of nano-particles and using the SLS
technique further, the size distribution can be measured accurately and is also
consistent with the results measured using the TEM technique. Based on the size
distribution obtained using the SLS or TEM technique and the relation between
the static and hydrodynamic radii, all the expected and measured values of
$g^{\left( 2\right) }\left( \tau \right) $ investigated are very well
consistent. Since the data measured using the DLS technique contains the
information of the optical and hydrodynamic properties of nano-particles
together, therefore the accurate size distribution cannot be obtained from the
experimental data of
  $g^{\left( 2\right) }\left( \tau \right) $ for an unknown sample. The
traditional particle information: apparent hydrodynamic radius and
polydispersity index measured using the DLS technique are determined by the
optical and hydrodynamic characteristics and size distribution together. They
cannot represent a number distribution of nano-particles in dispersion. Using
the light scattering technique not only can measure the size distribution
accurately but also can provide a method to understand the optical and
hydrodynamic characteristics of nano-particles.
