1. The problem statement, all variables and given/known data I need to calculate radiation power of ball in range 400nm-800nm. T=10000K d=1um. 2. Relevant equations I think I need to use Planck equation and integrate that. My equation in link: http://imgur.com/XbAUwJ8 3. The attempt at a solution I look for equations and laws and try to do my equation (above). If this is correct, I ask for help with calculate that.