ABSTRACT
As far as number distribution is concerned, particles are considered to be spherical, regardless of their shapes and densities. This assumption is necessary for the
discussion of particle statistics. There are two categories of spherical particles: monodisperse and polydisperse. The “size” of monodisperse particles is completely defined by a single parameter, the particle diameter
d
. Most particles, however, are polydisperse and have particle sizes that range over two or more orders of magnitude. This wide range of particle sizes even applies to the same particle source. For example, cigarette smoke contains tobacco particles ranging from less than 0.01
m
m
to larger than 1
m
m. Because of the wide range and the fact that the physical properties of particles are strongly dependent on particle size, it is necessary to characterize these size distributions accurately by statistical means.
