Basics on Light Scattering by Particles

This chapter introduces the basic concepts of the properties of electromagnetic waves, and the models and theories that describe the light scattering properties of small particles (droplets, bubbles, nanoaggregates, etc.) that are encountered in fluid mechanics and mechanical engineering problems. This chapter first describes the basic properties of electromagnetic waves interacting with linear materials. Then it discusses quantities and concepts commonly used to describe the elastic interaction of electromagnetic waves with particles. After presenting rigorous theories describing the absorption and scattering properties of highly symmetric particles (Lorenz-Mie theory (LMT) and Debye theory), the chapter explains asymptotic models that are computationally efficient but only valid for particles that are small or large with respect to the wavelength. Finally, the chapter talks about semi-analytical and numerical methods allowing us to model the optical properties of complex-shaped nanoparticles or nanoparticulate systems (the T-matrix method, the discrete dipole approximation and the Monte Carlo method).