Theoretical Models of Light Scattering and Absorption

When light interacts with a single particle, there are three possible outcomes: absorption, scattering, or transmission. In spectroscopy, one measures the remission from and/or transmission through a macroscopic sample. Such a sample might contain countless locations at which there is a change in refractive index, each of which gives rise to scattered light. This fact poses a challenge in building theoretical models applicable to spectroscopy: even if our theoretical understanding of single interactions is very good, the number of individual interactions is typically too big to make accounting for all of them realistic. This chapter presents an overview of modeling strategies that can be of use in near infrared spectroscopy. Recognizing that no one approach is uniformly applicable, care is taken to call attention to assumptions made in each modeling approach and limitations that are imposed by these assumptions.