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Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is considered radioactive. Three of the most common types of decay are alpha, beta, and gamma decay.
λ indicates the radioactivity decay constant in nuclear physics and radioactivity. This constant is very simply related (by a multiplicative constant) to the half-life of any radioactive material. In probability theory, λ represents the density of occurrences within a time interval, as modelled by the Poisson distribution. [14]
Half-life (symbol t ½) is the time required for a quantity (of substance) to reduce to half of its initial value.The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable atoms survive.
n (no standard symbol) = / / dimensionless dimensionless Radioisotope time constant, mean lifetime of an atom before decay τ (no standard symbol) = / s [T] Absorbed dose, total ionizing dose (total energy of radiation transferred to unit mass) D can only be found experimentally
The activity of a sample decreases with time because of decay. The rules of radioactive decay may be used to convert activity to an actual number of atoms. They state that 1 Ci of radioactive atoms would follow the expression N (atoms) × λ (s −1) = 1 Ci = 3.7 × 10 10 Bq, and so N = 3.7 × 10 10 Bq / λ, where λ is the decay constant in s ...
The constants listed here are known values of physical constants expressed in SI units; that is, physical quantities that are generally believed to be universal in nature and thus are independent of the unit system in which they are measured. Many of these are redundant, in the sense that they obey a known relationship with other physical ...
The unit of activity is the becquerel (symbol Bq), which is defined equivalent to reciprocal seconds (symbol s −1). The older, non-SI unit of activity is the curie (Ci), which is 3.7 × 10 10 radioactive decays per second. Another unit of activity is the rutherford, which is defined as 1 × 10 6 radioactive decays per second.
A quantity undergoing exponential decay. Larger decay constants make the quantity vanish much more rapidly. This plot shows decay for decay constant (λ) of 25, 5, 1, 1/5, and 1/25 for x from 0 to 5. A quantity is subject to exponential decay if it decreases at a rate proportional to its current value.