5. The ozone layer absorbs (a) blems 1. Calculate the activity in curies of 1 microgram of Th X with half life 3.64 days. (0.154 curie) 2. Calculate the time required for 10% of a sample of thorium to disintegrate. Given that the half life of thorium is 1.4 x 1010 years. (2.1 x 109 years) 3. The half life of radium is 3.82 days. What fraction of a freshly prepared sample of this nuclide will disintegrate in ten days? In one days? (0.837; 0.166) 4. If the half-lives of uranium-238, radium and radon are 4.5 x 10' yr, 1620 yr and 3.8 days respectively. Calculate the relative proportions of these elements in a uranium ore which has attained equilibrium and from which the radon is unable to escape. (4.7 x 1014, 1.56 x 105, 1) 5. Biologists have defined a "standard man" who contains, among other elements 18% carbon and 0.2% potassium. How many microcuries of 14C and of 40 will be present in an 80 kg man? (0.104, 0.13) vity due to 14C of 3.8 disintegrations per min gm- of carbon. What (11800 years)