Two plane coaxial disks are separated by a distance l = 0.80 m. the lower disk (a1) is solid with a diame- ter do = 0.80 m and a temperature t1 = 300 k. the upper disk (a2), at temperature t2 = 900 k, has the same outer diameter but is ring-shaped with an inner diameter di = 0.40 m.
a). find the view factor f2
b). assuming the disks to be blackbodies, calculate the net radiative heat exchange between them