Figure 49.11: Image observed in a kaleidoscope. (Credit: “Kaleidoscope Optics” at
http://www.4physics.com/phydemo/kaleidoscope/kaleidoscope-0.html. Image copyright © 4physics.com.)
just rotate the top mirror? Because if the top mirror were rotated, objects behind the observer would appear
upside-down. The entire instrument must be rotated to keep the image rightside-up.
49.8 The Kaleidoscope
Akaleidoscope(from the Greek
̨ o&—“beautiful,”ıo&—“form,” and
o!—“see”) is an optical
instrument invented by Scottish physicist David Brewster, whose purpose is to produce varying beautiful,
colorful patterns for the enjoyment of the user. One end of the kaleidoscope has a rotating disk containing
colorful objects like beads or glass. The tube of the kaleidoscope contains mirrors — typically three long
rectangular mirrors fastened together to form a prism whose cross section is an equilateral triangle. The user
holds the kaleidoscope up to a light source and looks through the mirrors toward the colored objects, and sees
the objects reflected multiple times in the mirrors, producing a pleasing colorful design. The design can be
modified by rotating the disk of colored objects, producing an endless variety of patterns.
Different mirror configurations are sometimes used to produce images with different symmetry patterns.
In one type of kaleidoscope, sometimes called theteleidoscope, the disk of colored objects is replaced by
a lens, so that patterns are formed from images of whatever objects are in the direction the instrument is
pointed.