1. Radiation is energy that travels through space in the form of waves or particles. There are two main types: ionizing radiation which can disrupt atoms and molecules, and non-ionizing radiation which does not have enough energy to do so. 2. Sources of radiation include natural background radiation like cosmic rays from space, radioactive elements in the ground and air, and internal radioactive isotopes in the body. Man-made sources include medical x-rays, nuclear power plants, consumer products, and fallout from nuclear weapons tests and disasters. 3. Ionizing radiation includes alpha particles, beta particles, gamma rays, and x-rays. They are able to ionize or change atoms and molecules and