temperature at which a black body in thermal equilibrium with its surroundings would have to be in order to duplicate the observed intensity of a grey body object at a frequency, temperatuur, mille juures peab olema ümbritsevaga termilises tasakaalus olev must keha, et dubleerida halli kehaobjekti täheldatud intensiivsust kiirgussagedusel, measure of the intensity of electromagnetic energy coming from a source