The size of each unit is directly proportional to the frequency of the energy's radiation. The impact of quanta upon certain metal surfaces cause the emission of electrons. The ratio of emittance of a given object and a blackbody at the same temperature. The ratio of emitted radiation to absorbed radiation is the same for all blackbodies at the same temperature. This law forms the basis for the definition of emissivity.
Hot blackbodies emit more energy per unit area than cool ones.