3 Transient conduction in a semi-infinite region is used to determine the thermal diffusivity of material. The procedure is to experimentally heat the surface of a thick plate which is initially at uniform temperature such that the surface is maintained at constant temperature. Measurement of surface temperature and the temperature history at a fixed location in the region provides the necessary data to compute the thermal diffusivity. [a] Show how the transient solution in a semi-infinite region can be used to determine the thermal diffusivity. [b] Justify using the solution for a semi-infinite region as a model for a finite thickness plate. [c] Compute the thermal diffusivity for the following data: T =initial temperature = 20C, T =surface temperature = 131 C, T(x,t) = 64C=temperature at location x and time t x = distance from surface = 1.2 cm t = time = 25 s