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convex




convex lens
A convex lens focuses parallel rays of light to a point
Curved outward, or having positive curvature, as in certain mirrors and lenses; the word comes from the Latin convexus for "vaulted." A biconvex lens has two convex surfaces, not necessarily with the same radii of curvature.

A figure, such as a polygon or a polyhedron, is said to be convex if every line segment that joins two interior points remains inside the figure. Similarly, a set is convex if it contains all the line segments connecting any pair of its points. Compare with concave.


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