This book presents a new didactical approach to the study of optics. It emphasizes the importance of elaborate new experimental demonstrations containing pictorial illustrations, computer simulations and models of optical phenomena in order to ensure a deeper understanding of wave and geometric optics. It includes problems focused on the pragmatic needs of students, secondary school teachers, university professors and optical engineers. A substantial part of this volume is devoted to thermal radiation and its properties, especially with partial coherence. The book contains detailed descriptions of demonstrational experiments.