Radioactive tracers are substances that contain a small amount of radioactive material. They are used in various fields, including medicine and environmental science, to track the movement of materials within systems. For example, in medical imaging, radioactive tracers can help doctors visualize organs and detect diseases by highlighting areas of interest in the body. In environmental studies, radioactive tracers can be used to study water flow and pollution. By introducing a tracer into a water source, scientists can monitor its movement and understand how contaminants spread. This technique is valuable for assessing the health of ecosystems and managing natural resources effectively.