1. The problem statement, all variables and given/known data Consider the electromagnetic radiation inside a kiln, with a volume of 1 m3 and a temperature of 1500 K. Calculate the radiation pressure inside the kiln. How does it compare with the air pressure? 2. Relevant equations PV = NkT 3. The attempt at a solution I got the total energy using U/V = 8π5(kT)4/15(hc)3 and got U = 3.83 kJ. To find the radiation pressure would I just divide the energy by c? Also, how do I find the air pressure if I don't have a value for N?