This is the first book to give a comprehensive and coherent account of the basic methods of characterizing a solid through its interaction with electromagnetic fields. The theoretical treatment focuses on the determination of the essential parameters of a solid (energy bands, energy levels, effective mass of electrons and holes etc.) from measured absorption coefficients, scattering data, magneto-optical results etc. The discussion is at an intermediate level and all the formulas are carefully deduced and explained. All types of solids (semiconductors, crystals, metals, etc.) are covered and the latest experimental results are also presented.