Question

The human body contains 0.20% natural potassium. K-40 represents 0.0117% of naturally occurring potassium. 1. What is the radioactivity due to K-40 for a person weighing 70 kg? 2. What is the radioactivity due to K-40 for all people on Erath?

Answer 1

Ans:- a). natural potassium in a person = (70*.2/100) * 1000 g= 140 g K-40 presents = (140*0.0117)/100 g =0.01638 g The potassium isotope is a radioactive isotope, K40. It is present in all potassium at a very low concentration, 0.0118 %. It has a very long half-life, 1,260,000,000 years. When it decays 89 % of the events give rise to the emission of a beta ray with maximum energy of 1.33 Mev. The other 11 % of the decays produce a gamma ray with an energy of 1.46 Mev. The 140 g of potassium in a normal male contains about 4400 Bq (or 120,000 pCi) of K40; that quantity produces a decay rate of about 4400 disintegrations per second.That means that 4400 radioactive K40 atoms decay and emit radiation in our bodies each second for as long as we live. Since potassium is found in the intracellular fluids, about 98 % of the potassium in the body is within cells. Thus at least 98 % of these disintegrations take place within body cells, and are potentially capable of altering the cell's DNA. b). Every person on earth carries essentially the same amount of potassium in their body, and always has.the radiation emitted by K40, beta rays and gamma rays is no different than the beta rays and gamma rays emitted by other radioactive sources, which might suggest that any such radiation, at a similar intensity, would not produce visible damage. To evaluate radioactivity over whole earth , multiply population of earth with the radioactivity of single human body . for detailed concept , see http://www.physics.isu.edu/radinf/natural.htm otherwise my answer have sufficient information for this this question . please Rate it