The surface corresponding to the region of obscuration when a solid is illuminated from a point light source (located at the radiant point). A disk is the shadow of a sphere on a plane perpendicular to the sphere-radiant point line. If the plane is tilted, the shadow can be the interior of an ellipse or a parabola.
Shadow
See also
Cork Plug, Projection, Stereology, Trip-LetExplore with Wolfram|Alpha
References
Croft, H. T.; Falconer, K. J.; and Guy, R. K. "What Can You Tell About a Convex Body from Its Shadows?" §A10 in Unsolved Problems in Geometry. New York: Springer-Verlag, pp. 23-24, 1991.Referenced on Wolfram|Alpha
ShadowCite this as:
Weisstein, Eric W. "Shadow." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Shadow.html