Abstract
The light from high intensity electrodes comes principally from the luminous gas confined within the hemispherical crater of the anode. The distribution of intensity in the beam formed by the source with an accurate paraboloidal reflector has a marked resemblance to the normal probability curve. This resemblance has been investigated, using all available data of known reliability, and the agreement between curve and test is remarkable. From both theory and test, it is known that the beam formation is influenced by the ratio of the focal length of a mirror to its diameter, and the standard form of mirror has been found to give the best agreement with the probability curve. Also, there is a certain operating latitude allowable in current for given electrodes, and within these limits the intensity curve is relatively unchanged in form. Three sizes of searchlight, 24″, 36″, and 60″ in diameter, have been investigated and all give the same distribution. From these facts, it seems that the probability curve is applicable throughout the range of standard high intensity practice, and with this in mind a test procedure is suggested that may lead to lower testing costs and increased accuracy. Several attempts at a theoretical derivation have failed, and the data are here presented solely as a complete collection of available field tests.
© 1948 Optical Society of America
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