ABSTRACT
This chapter gives the mathematized account of the many interesting phenomena that happen when light energy in the form of photons interacts with matter. Such phenomena include various forms of scattering and absorption of the photons depending both on the properties of the photons (energy, momentum, intensity) and the properties of matter (elemental composition, mass, charge, etc). The mathematical tools involve formalisms that enable reliable approximations such as time-dependent and time-independent perturbation theory, and Born approximation. Exact theories such as Dirac's relativistic quantum mechanics are also used. Succinctly, elastic scattering (Rayleigh, Thomson), inelastic scattering (Compton), photoelectric absorption of photons by matter and production of electron-positron pairs by photons traversing matter, are treated in this chapter.
