Investigate the linear attenuation coefficient of the Pb for photons of 1252.5 MeV, the average energy of the gammas (recall your task 5) from a 60Co source. The intensity at a distance of 10 cm from a 60Co source is 2.010^6 photons s1. a) Calculate the intensity of the source at 0.8 m. b) Calculate the intensity at 0.8 m if you also interpose a one-inch-thick shield of Pb.