2. Exponential drop of activity (i) Define activity and state its units. (ii) Explain the following terms: a. natural lifetime b. biological lifetime (when a radionuclide) is introduced to a living...

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Extracted text: 2. Exponential drop of activity (i) Define activity and state its units. (ii) Explain the following terms: a. natural lifetime b. biological lifetime (when a radionuclide) is introduced to a living organism c. effective half-life (iii) The radionuclide Y is used in nuclear imaging and it has a physical half-life of 6.5 hours. The biological half-life of this element is 7.6 hours. The initial activity the radionuclide administered to a patient is 2000 MBq. How many hours after the administration of the radiopharmaceutical will its will activity drop to 125 MBq ?