Henderson, C. Hanford (Charles Hanford), 1861-1941, Woodhull, John F. (John Francis), 1857-1941 · New York, D. Appleton and company · leaf 321
Fig. 197.—Umbra. Fig. 198.—Umbra and penumbra. Umbra and Penumbra.—In Fig. 198 let F represent aflame, and let a and b represent its extremities; c d is anopaque object, and ef a screen as before. The region intowhich no light may pass is cd gli. Around this there isa region ceg and dfh into which…
Physics
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