Radioactivity and Nuclear Energy
放射性和核能
Unit Overview
In this topic, nuclear processes are examined. Ionizing radiation is very useful in industrial and medical fields but at the same time is hazardous to us. Nuclear radiation comes from natural and artificial sources. It is essential for students to understand the origin of radioactivity, the nature and the properties of radiation. Students should also learn simple methods to detect radiation and identify major sources of background radiation in our natural environment. Simple numerical problems involving half-lives are performed in order to understand the long-term effects of some radioactive sources. The potential hazards of ionizing radiation are studied scientifically and in a balanced way by bringing in the concept of dosage. In the atomic model, the basic structure of a nuclide is represented by a symbolic notation. Students learn the concepts of isotopes. They are also introduced to fission and fusion, nature’s most powerful energy sources.
核心概念
X-rays as Ionizing EM Radiation
X射線與電離電磁輻射X-rays as short-wavelength ionizing electromagnetic waves with high penetrating power; how they are produced when fast electrons strike a heavy metal target; and common uses (and limits) of X-rays.
Alpha, Beta and Gamma Radiation
α、β、γ輻射的本質與性質Origin and nature of α, β and γ emissions; comparing penetrating power, range, ionizing ability, behaviour in electric and magnetic fields, and typical cloud-chamber tracks.
Radioactive Decay, Half-life and the Exponential Law
放射性衰變、半衰期與指數定律Unstable nuclides decay randomly; activity proportional to remaining nuclei; half-life from graphs or data; background radiation; exponential decay \(N = N_0 e^{-kt}\); linking decay constant \(k\) and half-life.