username5288572
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Could someone please explain why the answer is not cName:  16138698840752628904896978705734.jpg
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Nairrod
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You cannot deduce the activity of the sources as the number of atoms (or alternatively the mass) in each source is not given. You only have information on the radioisotopes and their half-lives. Remember that radioactivity is the number of decays per second (1 becquerel is 1 decay per second). The more atoms that you have of the unstable substance the more decays per second so the more radioactive the source (material) will be.If you assume, and the question does not state this, that the number of atoms of each radioisotope source starts at the same amount then initially thallium-210 will be most active but over time most of the thallium will decay so then at some later time iridium-192 will be the most active and later still, following a time period over which most of the iridium-192 has decayed, then cobalt-60 will be most active. The question neither states the initial amount of each radioisotope nor the time.
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