CBSE NOTES CLASS 12 PHYSICS
CHAPTER 13 NUCLEUS
Half-life of a radioactive element
The time in which half of the number of atoms present initially in any sample get decayed; is called half-life (T1/2) of that radioactive element.
Relation between half-life and disintegration constant is given by
Average life or mean life of a radioactive element(τ)
Average life or mean life (τ) of a radioactive element is the ratio of total life time of all the atoms and total number of atoms present initially in the sample.
The number of atoms left un-decayed after ‘n’ half-lives is given by