Optical device consisting of mirrors that reflect images of bits of coloured glass or other objects in a symmetrical geometric design through a viewer. The design may be changed endlessly by rotating the section containing the loose fragments. A simple kaleidoscope consists of two thin, wedge-shaped mirror strips touching along a common edge. The mirrors are enclosed in a tube with a viewing eyehole at one end. At the other end is a thin, flat box that can be rotated; it is made from two glass disks, the outer one ground to act as a diffusing screen. In this box are pieces of coloured glass, beads, etc. When the box is turned, the objects inside tumble into an arbitrary grouping, and when the diffusing screen is illuminated, the sixfold or eightfold multiplication creates a striking symmetrical pattern. The kaleidoscope was invented by Sir David Brewster c. 1816.

This entry comes from Encyclopædia Britannica Concise.
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