Physics1. a) radiation~ The spontaneous decay or disintegration of an unstable atomic nucleus accompanied by the emission of radiation.b) nuclear energy~ Energy released when atomic nuclei undergo a nuclear reaction such as the spontaneous emission of radioactivity, nuclear fission, or nuclear fusion. c) background radiation~ relatively constant low-level radiation from environmental sources such as building materials, cosmic rays, and radionucleids ingested into the body.d) nuclear fission~ Atomic nuclear processes involving the splitting of nuclei resulting in the release of energy. e) nuclear fusion~ The nuclear process by which several small nuclei combine to form a larger one whose mass is slightly less than the sum of the small ones.2. Two types of nuclear reactions can produce nuclear energy. Nuclear fusion is a process in which two light nuclei combine to form a single heavier nucleus. Nuclear fission is a process in which a heavy nucleus splits into two smaller nuclei.3. Alpha, beta and gamma radiation are produced when an unstable nucleus decays. Alpha particles are made up of 2 protons and 2 neutrons. This means they have a charge of +2 and a mass of 4. Alpha particles are relatively slow and heavy. they have a low penetrating power: you can stop them with a simple sheet of paper. Because they have a large charge, alpha particles strongly ionize other atoms. Beta particles have a charge of minus 1 and a mass of about 1/2000 of a proton. This means that beta particles are equal to one electron. They are fast and light. Beta particles have medium penetration power: they are stopped by aluminum foil or plastic such as Perspex. Beta particles ionize the atoms they pass through, but not as strongly as alpha particles. Gamma rays are waves, not particles. This means they have no mass or charge. Gamma rays have a high penetrating power: a thick sheet of metal such as lead or concrete is needed to reduce them significantly. Gamma rays do not directly ionize other atoms, although they can cause atoms to emit other particles which will then cause ionization.4. Advantages of using nuclear energy instead of energy produced by fossil fuels: The Earth has limited reserves of coal and oil. Nuclear power plants could still produce electricity when coal and oil become scarce.  Nuclear power plants require less fuel than those that burn fossil fuels. One ton of uranium produces more energy than that produced by several million tons of coal or several million barrels of oil.