Mie theory is a mathematical model that describes how light interacts with small particles, typically comparable in size to the wavelength of light. Developed by physicist Gustav Mie in 1908, it explains the scattering of light by spherical particles, helping to understand phenomena like the color of the sky and the appearance of clouds. The theory provides equations to calculate the intensity and direction of scattered light based on the particle's size, shape, and refractive index. It is widely used in fields such as meteorology, aerosol science, and optics to analyze how particles affect light propagation in various environments.