A problem of importance in radiation studies is that of defining the relationship of flux to distance traversed by a unidirectional beam of radiation in an attenuating medium. If the beam is monochromatic, the relationship is given by the Bouguer equation <i>i</i>=<i>i</i><sub>0</sub><i>e</i><sup>-<i>km</i></sup>, or <i>i</i>=<i>i</i><sup>0</sup><i>t<sup>m</sup></i>, where <i>i</i> is the flux of the beam at distance <i>m</i> from the beginning of the attenuating medium; <i>i</i><sub>0</sub> is the original or “primative” flux, corresponding to <i>m</i> equal to zero; <i>t</i> is the transmissivity, equal to <i>e</i><sup>-<i>k</i></sup>, where <i>k</i> is the attenuation coefficient. A method of computing <i>i</i><sub>0</sub> for heterochromatic radiation (having a logical basis in the Bouguer equation) is developed which involve measurements of the total heterocbromatic beam, no spectrometer measurements being involved. Theoretical accuracy is sampled.
TORRENCE H. MACDONALD, "Bouguer’s Law and Heterochromatic Radiation," J. Opt. Soc. Am. 52, 569-569 (1962)