I was trying to work out a question where there is a little sphere inside a big sphere with a perfect vaccuum inbetween.the big sphere been 0.13m dia. and 1550 degrees kelvin hot. The little sphere .1m dia. and 1500 degrees kelvin. All of the radiation from the little sphere hits the big but some from the big misses the small and hits itself.What is the net radiation between them ? Do you think you can work out the percentage of radiation that hits the small sphere from the big is proportional to the amount of angle that hits the little sphere from a point on the big sphere divided by 180 degrees?Both spheres are black bodies.