THE PHYSICAL CHARACTERS OF PENUMBRAL SHADOWS AND THEIR SIGNIFICANCE IN ROENTGENOGRAPHY
Paul M. Andrus · Canadian Journal of Research/Canadian journal of research · 1930
A new observation regarding the visual characters of penumbral shadows is recorded. It is pointed out that penumbral shadows appear to be laid down as a series of bands arranged serially as to density. This occurrence results in far-reaching effects in radiography as well as in other sciences concerned with the observation of images.