Half-life

  • number of
    half-lives
    elapsed
    fraction
    remaining
    percentage
    remaining
    0 11 100
    1 12 50
    2 14 25
    3 18 12 .5
    4 116 6 .25
    5 132 3 .125
    6 164 1 .5625
    7 1128 0 .78125
    ... ... ...
    n 1/2n 100/2n

    half-life (symbol t1⁄2) is the time required for a quantity to reduce to half of its initial value. the term is commonly used in nuclear physics to describe how quickly unstable atoms undergo, or how long stable atoms survive, radioactive decay. the term is also used more generally to characterize any type of exponential or non-exponential decay. for example, the medical sciences refer to the biological half-life of drugs and other chemicals in the human body. the converse of half-life is doubling time.

    the original term, half-life period, dating to ernest rutherford's discovery of the principle in 1907, was shortened to half-life in the early 1950s.[1] rutherford applied the principle of a radioactive element's half-life to studies of age determination of rocks by measuring the decay period of radium to lead-206.

    half-life is constant over the lifetime of an exponentially decaying quantity, and it is a characteristic unit for the exponential decay equation. the accompanying table shows the reduction of a quantity as a function of the number of half-lives elapsed.

  • probabilistic nature
  • formulas for half-life in exponential decay
  • in non-exponential decay
  • in biology and pharmacology
  • see also
  • references
  • external links

Number of
half-lives
elapsed
Fraction
remaining
Percentage
remaining
0 11 100
1 12 50
2 14 25
3 18 12 .5
4 116 6 .25
5 132 3 .125
6 164 1 .5625
7 1128 0 .78125
... ... ...
n 1/2n 100/2n

Half-life (symbol t1⁄2) is the time required for a quantity to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo, or how long stable atoms survive, radioactive decay. The term is also used more generally to characterize any type of exponential or non-exponential decay. For example, the medical sciences refer to the biological half-life of drugs and other chemicals in the human body. The converse of half-life is doubling time.

The original term, half-life period, dating to Ernest Rutherford's discovery of the principle in 1907, was shortened to half-life in the early 1950s.[1] Rutherford applied the principle of a radioactive element's half-life to studies of age determination of rocks by measuring the decay period of radium to lead-206.

Half-life is constant over the lifetime of an exponentially decaying quantity, and it is a characteristic unit for the exponential decay equation. The accompanying table shows the reduction of a quantity as a function of the number of half-lives elapsed.