Definition of activity (radioactivity)

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Photonics Dictionary

activity (radioactivity): Radioactivity refers to the spontaneous emission of radiation from the nucleus of an unstable atom. This emission occurs as the nucleus undergoes radioactive decay, which is a natural and random process. Here are the key points defining radioactivity:

Natural process: Certain isotopes of elements are unstable and tend to undergo radioactive decay to achieve a more stable state. This decay process involves the emission of particles or electromagnetic waves from the atomic nucleus.

Types of radiation:

Alpha radiation: Consists of helium nuclei (two protons and two neutrons) emitted from the nucleus.

Beta radiation: Involves the emission of electrons (beta particles) or positrons (positively charged particles).

Gamma radiation: High-energy photons emitted during nuclear reactions. Gamma rays are a form of electromagnetic radiation.

Radioactive decay: The process by which an unstable atomic nucleus loses energy by emitting radiation. Each radioactive isotope has a characteristic decay rate expressed as its half-life, the time it takes for half of the atoms in a sample to decay.

Sources of radioactivity:

Natural sources: Found in minerals, rocks, and cosmic rays from space.

Artificial sources: Produced in nuclear reactors, medical treatments, and industrial applications.

Health and environmental impacts: Exposure to high levels of radiation can damage cells and genetic material, leading to health risks such as cancer. Proper handling and disposal of radioactive materials are essential to minimize environmental contamination.

Measurement and units: Radioactivity is measured in units such as becquerels (Bq), which quantify the rate of radioactive decay (one decay per second), or curies (Ci), an older unit equivalent to 3.7 × 10¹⁰ Bq.

Radioactivity has significant applications in medicine (radiation therapy, medical imaging), industry (radiography, sterilization), and energy production (nuclear power), but requires careful management due to its potential hazards.

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