http://hyperphysics.phy-astr.gsu.edu/hbase/mod6.html#c4 This link shows the general plot of energy emitted by a blackbody against frequency. My two questions regarding this plot are: 1. Is the frequency in the plot the frequency of EM radiation emitted by the blackbody? 2. Why does the energy fall off after reaching a maximum? The explanation my book gave was somewhat confusing, it says "Plank's spectral energy density ultimately falls to 0, because at very high frequencies, there is not enough thermal energy to produce even one photon." If it's refering to the frequencies of the emitted EM radiation, wouldn't there still be photons present? Any help is appreciated.