Laurence, Lionel · London, School of Optics · leaf 27
eives light from S, but none from S, while Pu receiveslight from S, but none from S. The area u u receives light from neither S nor S, 14 SHADOWS AND PHOTOMETRY 15 If the light S is, or approximates to, a point, the shadow is mainly umbraand uniformly dark, as u u in Fig. 8. It becomes larger as… … When S and B are of equal size (Fig. 10), the umbra does not vary insize with its distance, but the penumbra increases as it is further away,because the penumbral cone diverges. When S is largei than B (Fig. 11), the umbra decreases with distance,since the umbral cone is convergent, while the…
Optics
Internet Archive · Gerstein Library, University of Toronto · Public Domain Mark 1.0. Free to use for anything.
