## prismn-sided polygons and n parallelograms. The word 'prism' comes from the Greek prizma, which relates
to cutting or sawing. A prism is a semiregular polyhedron if all of its faces are regular polygons. If the lateral surfaces of the prism are perpendicular to the base, it is said to be a right prism; otherwise, it is known as a oblique prism. If the base of a prism is a regular n-agon, it is said to be a regular n-sided prism. The distance between the base and the upper surface is called the altitude. The volume of a prism with base-area B and altitude h is V = B.h. A four-sided right prism is also called a right parallelepiped. A right parallelepiped whose altitude is equal to the edges of the base is a cube. A four-sided oblique prism is also called a parallelepiped. Prisms with equal altitudes have equal volumes. A prismoid resembles a prism but
has bases that are similar rather than congruent, and sides that are trapezoids
rather than parallelograms. An example of a prismoid is the frustum of a pyramid. A prismatoid is
a polyhedron with all its vertices lying in two parallel planes. ## Optical prisms
## Related categories• SOLIDS AND SURFACES• OPTIC AND OPTICAL PHENOMENA | |||||||||

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