A radioactive parent nuclide of type 1 with initial number of nuclei (N10) decays into a radioactive daughter of type 2. Assume initially no daughter nuclei are present (N20 = 0), show that the number of daughter nuclei at any later time t is: N, (t) = N. Three radioactive sources each have activities of 1 Ci at t = 0. Their half-lives are, respectively: 1 s, 1 h, and 1 d. (a) How many radioactive nuclei are present at t 0 in each source? (b) How many nuclei of each source at t = 1 s? (c) How many decay between t = 0 and t = 1 h? 147