Departments : Integrating Science in Your Classroom :

Kaleidoscope Swirl
By John Cowens

It's easy to create fantastic kaleidoscope views – all you need are mirrors, tape and something to look at

My bathroom at home is equipped with a large medicine cabinet that has three mirrored doors. When I adjust the two outer mirrors at certain angles, I can see multiple images of my head.

We can see objects in a mirror because photons bounce off those objects, hit the mirror and reflect back to our eyes from only one place on the mirror, and at only one angle.

Generally speaking, "the angle of incidence is equal to the angle of reflection." The incident ray is a ray approaching a surface. The reflected ray is the portion of the incident ray that leaves the surface at the point of incidence. The angle of reflection is the angle between the incident ray and the reflected ray.

kaleidoscope image of flowers

The view through a homemade kaleidoscope.

For an example of this, we'll turn our attention to kaleidoscopes. The kaleidoscope was invented in 1817 by a Scottish scientist, Sir David Brewster. We regard kaleidoscopes as beautiful, intriguing toys, but, in the world of business, designers have used kaleidoscopes to help create new patterns for rugs, wallpaper and fabrics.

How a kaleidoscope works
Most kaleidoscopes work on the principle of multiple reflection. Two rectangular glass plates on the inside of the tube serve as mirrors. They run the entire length of the tube and slant toward each other, usually at an angle of 45" or 60". At the far end of the kaleidoscope are two more plates, one made of clear glass and the other of ground glass. The clear glass is closer to the eye hole. Beads and pieces of colored glass are placed between the plates and are reflected in the mirrors. The plate of ground glass throws the reflections in different directions, forming patterns. When the viewer turns the kaleidoscope, the colored beads and glass shift position and the reflected patterns change.

When three rectangular mirrors of the same dimensions are arranged to form an equilateral triangle, rays of light from an object will form multiple images due to the reflections from the mirrors. The equilateral triangle formed by the mirrors has three equal angles of 60" and the sides of the triangle have equal lengths.

Making a simple kaleidoscope
Materials:

  • three rectangular mirrors 2" x 10" (5 cm x 25 cm)

  • duct tape

  • small colorful items such as glitter, confetti, etc.

  • small resealable plastic bag

  • white paper or cardboard

a boy and a girl demonstrate a kaleidoscope

An equilateral triangle made from three long, rectangular mirrors wrapped with duct tape makes a simple kaleidoscope.

Procedures:

  1. Hold the three mirrors together, facing each other, to form an equilateral triangle.

  2. Use a few small pieces of tape to hold the mirrors together, then wrap large strips of duct tape around the mirrors completely to make the outer covering of the kaleidoscope.

  3. Hold the kaleidoscope and look through it at various objects.

  4. Hold the kaleidoscope above the piece of white cardboard and look through it. Put an object such as a coin, or the small bag filled with glitter or confetti, on the white cardboard. Observe the images reflected in the mirrors.

Questions
How many images did you see? Did they appear to be the same size as the actual objects? Would the kaleidoscope work properly if the mirrors were angled at 30", 60" and 90"? If so, what would happen to the images?

Extensions

  • Instead of using three mirrors to form an equilateral triangle, try using two mirrors and a strip of black cardboard to form the equilateral triangle. What changes occur when you look through this type of kaleidoscope?

  • Instead of using an equilateral triangle of mirrors inside the kaleidoscope, would the kaleidoscope work properly if the mirrors were angled at 30", 60" and 90"? If so, what happens to the images?

For further reading

  • The Kaleidoscope Book: A Spectrum of Spectacular Scopes to Make by Thom Boswell (Sterling, 1995, ISBN: 0-806-98371-X).

  • The Kids' Book of Kaleidoscopes by Carolyn Bennett (Workman, 1994, ISBN: 1-563-05638-0).

  • Kaleidoscope Math by Cindi and Jim Mitchell (Scholastic, 2003, ISBN: 0-439-08675-2).

  • Simple Kaleidoscopes: 24 Spectacular Scopes to Make by Gary Newlin (Lark Books, 1996, ISBN: 0-806-93155-8).

Online explorations
You and your students can find out more about kaleidoscopes by visiting these websites:

John Cowens teaches science at Fleming Middle School in Grants Pass, OR.

February 2004, Vol.34, No.5