Topic overview

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Radioactive decay includes alpha, beta-minus, beta-plus, electron capture, gamma emission and isomeric transition. Each mode has distinct emissions and shielding needs: alpha particles have high linear energy transfer but limited penetration, while gamma photons penetrate deeply. Half-life describes the time for activity to fall by half; the decay constant and exponential decay equation express how activity changes over time. The topic also distinguishes activity, absorbed dose, equivalent or effective dose, and exposure, with their associated units. Radiation weighting factors relate radiation type to biological effect. Together, decay behavior, dosimetry and shielding provide a foundation for considering radionuclide properties in clinical use and radiation protection.