Scattering by a Small Particle

Small particles (solvent molecules and monomers constituting the polymer) suspended in vacuum can scatter the light. They are called scatterers. An electromagnetic wave, also called radiation, enters the isotropic particle to cause polarization in the direction of the electric field of the incident wave (Fig. 2.34). The polarization is a displacement of the spatial average of the positively charged nuclei with 

At a distance r from the particle and at angle O from the vertical, the intensity I of 

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The intensity of the light scattered by a small particle is proportional to the sixth power of its radius, and the total scattered intensity will be obtained by summing over all particles. In order to simplify the analysis of the results, it has been assumed that all particles are consumed at similar rates, so that the number does not change, and that the particles are of a similar size, so that the summation may be omitted. The measured intensity I is expressed in terms of the particle number density (n) and the radius (a) as ... 

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