radioaktiv

Radioaktiv (radioactive) describes materials whose atomic nuclei are unstable and decay over time, releasing radiation as they transform into more stable configurations. The emitted radiation can be in the form of alpha particles, beta particles, gamma rays, or neutrons, depending on the decay process. Radioactive decay is probabilistic and characterized by a half-life, the time it takes for half of a sample to decay.

Measurements associated with radioactivity include activity, measured in becquerels (Bq), representing decays per second. The absorbed dose, measuring energy deposited in matter, uses the gray (Gy). For biological impact, the equivalent dose and effective dose use the sievert (Sv) to reflect different radiations and exposed tissues. Historically, non-SI units such as the roentgen were used for exposure, but SI units are standard today.

Radioactivity occurs naturally and artificially. Natural sources include unstable isotopes in the Earth’s crust (such as uranium and thorium) and radon gas, as well as cosmic radiation. Human activities generate artificial radioactivity through nuclear reactors, medical isotopes, industrial radiography, research, and weapons development.

Applications of radioactivity cover medicine (diagnostic imaging, radiotherapy), sterilization of medical devices, industrial non-destructive testing, and scientific research. Radiometric dating, notably carbon-14 dating, uses natural radioactivity to estimate ages in archaeology and geology.

Safety and regulation aim to minimize exposure by applying the principles of time, distance, and shielding, along with monitoring and protective standards. The discovery of radioactivity in 1896 by Henri Becquerel, followed by work from Marie and Pierre Curie, established a foundation for both beneficial uses and important safety considerations.