The Reflection Factors of Tungsten at Incandescent Temperatures
W. Weniger, A. H. Pfund
A direct method has been developed for measuring the reflection factors of substances at incandescent temperatures. Curves are given showing the variation in the reflection factor of tungsten for wave-lengths from 0.67μ to 4.0μ and for temperatures up to 2067°K. The reflection factor of tungsten was found to increase with temperature for wave-lengths less than about I.27μ and to decrease with temperature for wave-lengths longer than this. The transition from the approximately constant positive temperature coefficient in the visible to the approximately constant negative coefficient in the infra-red takes place in the rather narrow region lying between about 0.7μ and 2.0μ. The numerical values of the reflection factor agree fairly well with Worthton's values in the visible and with the theoretical equation first applied to long wave-lengths by Hagen and Rubens, beyond 2μ in the infra-red. © 1919 The American Physical Society.
