Radioactivity and Nuclear Decay - SS2 Physics Lesson Note
Radioactivity is the spontaneous emission of particles or radiation from unstable atomic nuclei. It was first discovered by Henri Becquerel in 1896, and further explored by Marie Curie and other scientists. The phenomenon of radioactivity revolutionised our understanding of the atom and led to important advancements in various fields of science and technology.
Radioactive decay is the process by which unstable atomic nuclei transform into more stable configurations. It occurs due to the inherent instability of certain isotopes, which have an imbalance between the number of protons and neutrons in their nuclei. The three main types of nuclear decay are alpha decay, beta decay, and gamma decay.
Alpha Decay:
In alpha decay, an alpha particle consisting of two protons and two neutrons is emitted from the nucleus. This results in a decrease of the atomic number by 2 and the mass number by. Alpha decay is common in heavy elements, such as uranium and thorium.
Beta Decay:
Beta decay involves the emission of beta particles, which can be either beta-minus (β-) particles or beta-plus (β+) particles. In beta-minus decay, a neutron in the nucleus is converted into a proton, and an electron (beta particle) and an antineutrino are emitted. In beta-plus decay, a proton in the nucleus is converted into a neutron, and a positron (beta particle) and a neutrino are emitted. Beta decay results in a change in the atomic number but no change in the mass number.
Gamma Decay:
Gamma decay involves the emission of gamma rays, which are high-energy photons. Unlike alpha and beta decay, gamma decay does not result in a change in the atomic number or mass number. Gamma rays are emitted to release excess energy from the nucleus following alpha or beta decay.
Radioactive decay is a random process, and the rate of decay of a radioactive substance is described by its half-life. The half-life is the time taken for half of the radioactive nuclei in a sample to decay. Different radioactive isotopes have different half-lives, ranging from fractions of a second to billions of years.
Applications of Radioactivity:
- Medicine: Radioactive isotopes are used in diagnostic imaging (such as PET scans), radiation therapy for cancer treatment, and sterilisation of medical equipment.
- Energy Generation: Nuclear power plants harness the energy from controlled nuclear reactions to generate electricity.
- Dating Techniques: Radioactive isotopes, such as carbon-14, are used for radiometric dating to determine the age of archaeological artefacts and geological materials.
- Industrial Applications: Radioactive isotopes are utilised in various industrial processes, such as thickness measurement, gauging, and quality control.
- Research and Development: Radioactive tracers are employed to study chemical reactions, biological processes, and environmental movements.
It is important to handle radioactive materials with proper precautions to minimise radiation exposure and ensure safety. Regulatory bodies and international organisations establish guidelines and regulations for the use and disposal of radioactive substances to protect human health and the environment.