Young, George, jr, Baxter, Hubert Eugene, joint author · New York, The Macmillan Co. · leaf 260
tercepting the hght; and (3) a 1 Exercise Sheets to accompany this chapter are given on pp. 304-309. 242 XII, § 203] SHADES AND SHADOWS 243 receiving surface on which the shadow falls. These factorsare illustrated in Fig. 225. From the source of light L, issuerays that illuminate the sphere and the… … Fig. 225 of this cone which lies between the sphere and P, is a darkspace called the umbra. The line of tangency between the cone and the sphere iscalled the shade line, or separatrix, and all that part of the spherewhich lies within the umbra is said to be in shade. The inter-section of the…
Geometry, Descriptive
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