This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nuclear Medicine, Subject name: Radiology
Half life of Co60 is- 
Select and explain. 
A. 74.5 years, B. 5.2 years, C. 30 years, D. 2.6 years
B: 5.2 years
Answer: B: 5.2 years 
Explanation: 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