Radioactive decay of unstable atomic nuclei is a fi rst-order process. Th e half-life for the (fi rst-order) radioactive decay of 14C is 5730 a (1 a is the SI unit 1 annum, for 1 year; the nuclide emits b particles, high-energy electrons, with an energy of 0.16 MeV). An archaeological sample contained wood that had only 69 per cent of the 14C found in living trees. What is its age

answer: semi-infinite solid initially at a uniform temperature of 400 ◦c is cooled at its surface by convection. the cooling fluid at a constant temperature of 200 ◦c has a convective coefficient (ha) of 250 w/m2.k. the physical properties of the solid: k = 20 w/m.k and α = 4 * 10-5  m2/s. using δx = 0.04 m and δt = 10 s. write the finite difference equations describing the transient heat transfer of the first five δx and the temperature profile after 30 s.