Quantum Physics

Aerial view of a nuclear power plantthat generates electrical power.Energy is generated in such plantsfrom the process of nuclear fission, inwhich a heavy nucleus such as 235 Usplits into smaller particles having alarge amount of kinetic energy. Thissurplus energy can be used to heatwater into high pressure steam anddrive a turbine.Nuclear PhysicsIn 1896, the year that marks the birth of nuclear physics, Henri Becquerel (1852–1908)discovered radioactivity in uranium compounds. A great deal of activity followed this discoveryas researchers attempted to understand and characterize the radiation that we now knowto be emitted by radioactive nuclei. Pioneering work by Rutherford showed that the radiationwas of three types, which he called alpha, beta, and gamma rays. These types are classifiedaccording to the nature of their electric charge and their ability to penetrate matter. Laterexperiments showed that alpha rays are helium nuclei, beta rays are electrons, and gammarays are high-energy photons.In 1911 Rutherford and his students Geiger and Marsden performed a number of importantscattering experiments involving alpha particles. These experiments established the ideathat the nucleus of an atom can be regarded as essentially a point mass and point charge andthat most of the atomic mass is contained in the nucleus. Further, such studies demonstrateda wholly new type of force: the nuclear force, which is predominant at distances of less thanabout 10 14 m and drops quickly to zero at greater distances.Other milestones in the development of nuclear physics include• the first observations of nuclear reactions by Rutherford and coworkers in 1919, in whichnaturally occurring particles bombarded nitrogen nuclei to produce oxygen,• the first use of artificially accelerated protons to produce nuclear reactions, by Cockcroftand Walton in 1932,• the discovery of the neutron by Chadwick in 1932,• the discovery of artificial radioactivity by Joliot and Irene Curie in 1933,• the discovery of nuclear fission by Hahn, Strassman, Meitner, and Frisch in 1938, and• the development of the first controlled fission reactor by Fermi and his collaboratorsin 1942.In this chapter we discuss the properties and structure of the atomic nucleus. We start bydescribing the basic properties of nuclei and follow with a discussion of the phenomenon ofradioactivity. Finally, we explore nuclear reactions and the various processes by which nuclei decay.Courtesy of Public Service Electric and Gas CompanyCHAPTER29O U T L I N E29.1 Some Properties of Nuclei29.2 Binding Energy29.3 Radioactivity29.4 The Decay Processes29.5 Natural Radioactivity29.6 Nuclear Reactions29.7 Medical Applicationsof Radiation29.8 Radiation Detectors939