Radioactivity And Nuclear Decay - SS2 Physics Lesson Note
Radioactivity is the spontaneous emission of radiation from the nucleus of an atom. It occurs in certain types of unstable atomic nuclei, known as radioactive isotopes. Radioactive decay is the process by which these unstable nuclei transform into more stable configurations, releasing energy in the form of radiation.
Types of Radioactive Decay:
There are three main types of radioactive decay:
- Alpha Decay: In alpha decay, an atomic nucleus emits an alpha particle, which consists of two protons and two neutrons. This reduces the atomic number of the nucleus by 2 and the mass number by 4.
- Beta Decay: Beta decay involves the emission of either a beta-minus particle (an electron) or a beta-plus particle (a positron) from the nucleus. Beta-minus decay increases the atomic number by 1, while beta-plus decay decreases it by 1.
- Gamma Decay: Gamma decay occurs when an excited nucleus releases energy in the form of gamma rays, which are high-energy photons. Gamma decay does not change the atomic or mass number of the nucleus.
Half-Life:
The half-life of a radioactive isotope is the time it takes for half of the radioactive nuclei in a sample to decay. It is a characteristic property of each isotope and can range from fractions of a second to billions of years. Half-life is important for determining the decay rate and the amount of remaining radioactive material over time.
Decay Equations:
Radioactive decay can be mathematically described using decay equations. For example, the decay of a radioactive nucleus A can be represented as A -> B + radiation, where B is the resulting nucleus after the decay. The decay equation also accounts for the type of radiation emitted, such as alpha, beta, or gamma particles.
Radioactive Dating:
Radioactive decay is used in radiometric dating techniques to determine the age of rocks, fossils, and archaeological artefacts. By measuring the ratio of parent isotopes to daughter isotopes in a sample and knowing the half-life of the parent isotope, scientists can calculate the age of the sample.
Nuclear Reactions and Nuclear Energy:
Radioactive decay is a form of nuclear reaction. It involves changes in the structure of atomic nuclei, which release large amounts of energy. This energy can be harnessed for various applications, including generating nuclear power in nuclear reactors.
Radiation Hazards and Safety:
Radioactive materials can pose health risks due to their ability to ionise atoms and damage biological tissue. Proper handling, storage, and disposal of radioactive substances are crucial to minimise radiation exposure. Protective measures, such as shielding and monitoring devices, are used to ensure safety in radioactive environments.
Radioactivity and nuclear decay are fundamental concepts in nuclear physics. They have wide-ranging applications in fields such as medicine, energy production, archaeology, and environmental monitoring. Understanding the principles of radioactivity enables us to utilise its benefits while ensuring safety and minimising potential risks.