Atomic Structure and Radioactivity - SS1 Physics Past Questions and Answers - page 5

Half-life is the time it takes for half of the radioactive nuclei in a sample to undergo decay. It is a characteristic property of each radioactive isotope. By measuring the amount of radioactive isotope remaining in a sample and knowing its half-life, we can determine the age of objects. The age is calculated by comparing the ratio of the remaining radioactive isotope to the original amount present in the sample. The more half-lives that have passed, the smaller the ratio, indicating an older age.

Gamma decay involves the emission of high-energy electromagnetic radiation called gamma rays. Unlike alpha and beta decay, gamma decay does not change the atomic number or mass number of the nucleus. Gamma rays are emitted to release excess energy from an excited nucleus, transitioning it to a lower energy state. The emission of gamma radiation occurs alongside alpha or beta decay, but it does not involve the release of any particles. Therefore, the atomic number and mass number remain unchanged.

Radioisotopes have significant applications in medicine. In diagnostic imaging, radioisotopes are used to visualise organs, tissues, and physiological processes inside the body. For example, technetium-99m is commonly used in nuclear medicine scans to diagnose heart conditions, bone disorders, and certain cancers. It emits gamma radiation, which can be detected by specialised imaging devices.

In cancer treatment, radioisotopes are utilised in a process called radiation therapy. High-energy radiation. This targeted radiation damages the DNA of the cancer cells, preventing them from dividing and growing. Radioisotope-based brachytherapy is another technique where radioactive sources are placed directly inside the body near the tumour site.

Radioisotopes play a crucial role in various industrial applications. They are used for quality control purposes, such as ensuring the integrity and safety of manufactured products. For instance, radioisotopes can be employed to detect leaks in pipelines or identify structural defects in materials. By measuring the radiation emitted by the radioisotopes, flaws or inconsistencies can be detected, ensuring high-quality standards.