<prompt> Half life of Co60 is-74.5 years5.2 years30 years2.6 years  <response>: Ans. is b i.e., 5.2 years Half life of cobalt - 60 is 5.2 years.Cobalt - 60 It is an artifical radioactive cobalt. It has a half life of 5.2-5.3 years. It is used as a teletherapy source as well as in brachytherapy. It decays, emits beta and gamma rays, and has to be replaced at regular intervals of about 4-5 years. It is produced from cobalt - 59, which is a natural nonradioactive substance. It decays to produce nickel, which is not radioactive. It has atomic number - 27. Its atomic weight is 58.93 