Abstract: Near UV to mid-infrared light measurements are highly advantageous in a number of domains of surface analysis. While less direct than high energy probes, light-based measurements are largely nondestructive, relatively safe, and can be conducted in air. However, scattering complicated these measurements by introducing spectral features related to the sample topography rather than the materials present. Computational modeling of light scattering can significantly improve the information that can be obtained from optical surface analysis methods. I will describe two such examples from my research. The first and older example makes use of highly regular structures on integrated circuit wafers to extract surface topography at very high accuracies. The second and more recent example looks at mid-infrared scattering of irregular distributions of particles on surfaces for remote identification of trace chemicals. In both cases, use of accurate computational electromagnetic scattering models was critical.