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# Lens (geometry)

In geometry, a **lens** is a biconvex (convex-convex) shape comprising two circular arcs, joined at their endpoints. If the arcs have equal radii, it is called a **symmetric lens**, otherwise is an **asymmetric lens**.
A concave-convex shape is called a lune. The vesica piscis is one form of a symmetrical lens; the term is also used for lenses generally.

In common usage, the term lens is also used to describe the shape of a three-dimensional object obtained by rotating a two-dimensional lens about its narrow axis of symmetry. Such a shape is described as **lenticular** and is most commonly used for focussing and dispersement of electromagnetic radiation.

## See also

## References

- Eric W. Weisstein. "Lens".
*MathWorld*. Retrieved June 13, 2005. which in turn cites- Pedoe, D. (1995). "Circles: A Mathematical View, rev. ed.".
*Washington, DC: Math. Assoc. Amer*. - Plummer, H. (1960).
*An Introductory Treatise of Dynamical Astronomy*. York: Dover. - Watson, G. N. (1966).
*A Treatise on the Theory of Bessel Functions, 2nd ed*. Cambridge, England: Cambridge University Press.

- Pedoe, D. (1995). "Circles: A Mathematical View, rev. ed.".

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