Half-life

Half-life in Radioactive Decay

Definition of Half-life

  • Half-life is a term used in nuclear physics to describe the time required for half of the atoms in a sample of a radioactive substance to decay.
  • It is important to remember that half-life is not the time it takes for all of the atoms in the sample to decay, but just half of them.

Unpredictability of Individual Atoms

  • While the decay of an individual atom cannot be predicted, the rate of decay of a large number of atoms is predictable and constant. This is because decay is a probability based process.
  • This is why the concept of half-life is useful: it gives a precise measure of how quickly a radioactive element is decaying.

Relationship with Decay Constant

  • The half-life of an isotope is directly linked to its decay constant. The decay constant of an isotope represents the probability that an atom will decay per unit time.
  • Mathematically, the half-life (t₁/₂) is related to the decay constant (λ) as: t₁/₂ = 0.693/λ

Calculating Half-life

  • The half-life of a substance can be calculated if the initial number of radioactive atoms and the number of those atoms that remain after a certain time period are known.

Uses of Half-life

  • Half-life has practical applications in various fields. In medicine, it is used to determine the duration that a radioactive drug will stay effective in the body.
  • In archaeology and geology, it is used for dating ancient artifacts and geological formations (radiometric dating).
  • In nuclear power, understanding the half-life of radioactive waste helps in managing and containing the waste.

Safety Concerns

  • Substances with short half-lives are more radioactive (emit more radiation per unit time) than those with long half-lives. Therefore, handling substances with short half-lives must be done with extreme caution.
  • In contrast, substances with long half-lives continue to be a source of radiation for a long time. This impacts their disposal and containment.

Remember that the concept of half-life can seem complex, but a clear understanding of it helps provide insights into the fascinating and practical world of nuclear physics.