Needs["BlackBodyRadiation`"]

BlackBodyProfile[300 Kelvin,400 Kelvin,500 Kelvin,PlotRange->{{0,2.0*10^-5},All}, LabelStyle -> Larger, ImageSize -> Scaled[0.8]] // Quiet

BlackBodyProfile[4000 Kelvin,5000 Kelvin,6000 Kelvin,PlotRange->{{0,2.0*10^-6},{0,1.1*10^14}}, LabelStyle -> Larger, ImageSize -> Scaled[0.8]] // Quiet