MIT lecturer R. Scott Kemp opens the technical core of 22.04, Social Problems of Nuclear Energy, with a grounding in how radiation actually works. The lecture covers how ionizing radiation interacts with matter and living tissue, laying out the physical mechanisms before turning to how scientists translate those mechanisms into measures of risk. Kemp treats this as foundational material for the course's later debates over nuclear policy, since arguments about safety, regulation, and public fear only make sense once the underlying physics and biology are clear. Expect a chalk-and-talk style lecture aimed at MIT undergraduates, part of a semester-long course that otherwise deals with the politics and sociology of nuclear power, with this session serving as the technical anchor for everything that follows.