Abstract
The spectra of secondary electrons produced by a Co60 gamma-ray source have been measured at distances of 10, 20, 41.6, 81.6, 121.6, and 161.6 cm in a large tank of water. The pulse-height distribution representing the energy lost in an anthracene crystal was determined for each separation of detector and source. The shape of the spectrum was found to change appreciably with distance. The results agree remarkably well with theoretical predictions.