The course deals with the interaction with matter for photons and charged particles. The interaction cross-sections andtheir dependence on photon energy, atomic number of the medium, and density are described in detail. hte course alsocovers the Bethe-Bloch mass stopping power, bremsstrahlung, and the parameter dependence of the cross-sections. Thecourse also covers the principle for production of X-rays in the x-ray tube. An overview is given of relevant Monte Carlotechniques. The course includes compulsory laboratory work.