(20 Points) The diffusion constant of iron in FCC iron is 22106m2/s, and activation energy is 268kJ/mol. What is the self-diffusivity, D, of iron solute in FCC iron at 900C?(R=8.314J/mol) 4) (25 Points) a) When light passes from a high index of refraction medium to a low index of refraction medium, there is a critical angle of incidence, c. Beyond which no light passes the interface. This c is defined at refraction=90. What is c for light passing from silica glass to air? 1 Note that 1 and r are the angles of incidence and refraction, respectively. Refractive index of silica glass (SiO2) is 1.458