A small anodized aluminum block at 35°C is heated in a large oven whose walls are diffuse and gray with ɛ = 0.85 and maintained at a uniform temperature of 175°C. The anodized coating is also diffuse and gray with ɛ = 0.92. A radiation detector views the block through a small opening in the oven and receives the radiant energy from a small area, referred to as the target, A_t, on the block. The target has a diameter of 3 mm, and the detector receives radiation within a solid angle 0.001 sr centered about the normal from the block.

  (a) If the radiation detector views a small, but deep, hole drilled into the block, what is the total power (W) received by the detector?

  (b) If the radiation detector now views an area on the block surface, what is the total power (W) received by the detector?