The half-life cobalt 60 is:
a. A half-life is the interval of time required for one-half of the atomic nuclei of a radioactive sample to decay (change spontaneously into other nuclear species by emitting particles and energy), or, equivalently, the time interval required for the number of disintegrations per second of a radioactive material to decrease by one-half. Eg. Cabolt -60 has a half life of 5.26 years.
b. Half-lives are characteristic properties of the various unstable atomic nuclei and the particular way in which they decay.
c. Alpha and beta decay are generally slower processes than gamma decay.
d. Half-lives for beta decay range upward from one-hundredth of a second and, for alpha decay, upward from about one-millionth of a second. Half-lives for gamma decay may be too short to measure (around 10-14 seconD., though a wide range of half-lives for gamma emission has been reported.