Kaleidoscope

A kaleidoscope is an optical instrument with two or more reflecting surfaces inclined to each other in an angle, so that one or more (parts of) objects on one end of the mirrors are seen as a regular symmetrical pattern when viewed from the other end, due to repeated reflection. The reflectors (or mirrors) are usually enclosed in a tube, often containing on one end a cell with loose, colored pieces of glass or other transparent (and/or opaque) materials to be reflected into the viewed pattern. Rotation of the cell causes motion of the materials, resulting in an ever changing viewed pattern.

Coined in 1817 by Scottish inventor David Brewster, "kaleidoscope" is derived from the Ancient Greek (kalos), "beautiful, beauty", (eidos), "that which is seen: form, shape" and (skopeō), "to look to, to examine", hence "observation of beautiful forms."

A kaleidoscope operates on the principle of multiple reflection, where two or more reflectors are placed at an angle to one another. When the eye is placed at one end of the reflectors, the original view from the aperture on the other side is multiplied into a symmetrical mosaic pattern. A two-mirror kaleidoscope yields a circular pattern isolated against a solid black background, while the three-mirror equilateral triangle type yields an infinite pattern that fills the entire visual field.

Inventor David Brewster described three conditions for the kaleidoscope to produce "perfectly beautiful and symmetrical forms":

A proper kaleidoscope image can be achieved with a convex lens of such a focal length that the images of all surrounding objects were distinctly formed at the end of the reflectors and thus introduced into the reflected pattern.

An "object-box" (or cell) on the ends of the reflectors can hold selected objects to be viewed in the reflected pattern. Colorful transparent shapes (for instance pieces of glass or colored fluids moving in transparent containers) to create beautiful patterns. Objects smaller than the aperture create a spotted appearance of the pattern. Larger opaque objects and darker colors don't transmit much light and are usually avoided. If objects, fragments and/or liquids are loosely placed inside the cell and tumble when the cell is rotated, motion and change of colors and shapes can be introduced into the viewed pattern.

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