11 - Size, shape, composition, and structure of microparticles from light scattering

Summary

Introduction

When light impinges on a small particle, a fraction of the incoming light power is redirected in a process called the scattering of light. The angular distribution of intensity of the scattered light depends on the size, shape, orientation, composition, and structure of the particle.

The scattered light thus carries information about these characteristics of the particle. The use of light as a probe permits nondestructive characterization of a particle. The light intensity (photon flux) and wavelength (photon energy) are usually too low to damage the particles, even delicate biological cells. The scattered light can be measured in situ; thus the particles need neither be isolated from their natural environment nor specially prepared. In contrast, the preparation required by many other methods often modifies the particles and may render them unusable for further studies. Since the scattered light can be measured continuously, the temporal changes in particle characteristics can also be determined.

As with any other characterization method, the use of light scattering has its limitations. The information about the particle characteristics carried by the scattered light is encoded in a complex manner and often cannot be fully retrieved using currently available techniques. In addition, the scattered light can be extremely weak and may need sophisticated detection systems and time to be measured accurately.

The purpose of this paper is to introduce the reader to light scattering by small particles, its dependence on the particle characteristics, and its possible uses in oceanography and marine geology.