A sealed sample of a radioactive nuclide contains N0=1000 nuclei at t=0. After 18 minutes only 125 nuclei remain undecayed.
(a) Calculate the decay constant of the nuclide in min−1.
(b) Determine its half-life in minutes.
(c) How long (from t=0) will it take for the activity of the sample to fall to 10 % of its initial value?
(d) How many nuclei will be left undecayed at the instant found in part (c)?