Look Into Infinity
Images of images of images can repeat forever.
If you have ever been between two mirrors that face each other, such as in a barber shop
or a beauty salon, you will befamiliar with the seemingly endless line of images fading
into the distance. The Look Into InfinitySnack recreates this effect.
2 square pieces of plexi-mirror measuring 12 x 12 inches (30 x 30 cm). (Available
from plastics stores. Mirror size is not crucial. You can substitute a 12 x 12 inch [30 x 30
cm] glass mirror tile or any two mirrors for the plexi-mirror. See To Do and Notice.)
Some kind of stand. (See Assembly.)
Adult help.
(15 minutes or less)
Cut a hole about 1 inch (2.5 cm) in diameter near the center of one of the mirrors. You
can use a hole saw, or you can have this done for you at the plastics store. You can get
the effect without the hole, but the hole gives a more interesting perspective. If you don't
care about the hole, you can use glass mirror tiles instead of a plexi-mirror. You can even
create the hole on a glass mirror tile by scraping away the silver backing.
Stand the mirrors so that their reflecting surfaces face each other and are parallel to each
other. The mirrors can be anywhere from a few inches to a foot apart. You can make a
wooden stand for each mirror by cutting a slit along the length of the flat side of a piece
of 1 x 4 inch (2.5 x 10 cm) pine. Then slip the mirror into the slit. You can also stand
each mirror between two pieces of wood held together by rubber bands, or place two full
softdrink cans (or any heavy objects) so that one is on each side of the mirror, supporting
it.
(5 minutes or more)
With the reflecting surfaces facing each other, look through the hole into the space
between the mirrors. (If you didn't bother making a hole, just look over the top of one
mirror.) You can also try placing either your finger or some other object between the
mirrors.
If you place an object between the mirrors, notice that there is a repetitious pattern in the
orientation and spacing of the images. Objects with contrasting colors on the front and
back (such as red and white) show this well. Successive images alternate from front view
to back view. If the original object is closer to one mirror than to the other, the distance
between successive images will alternate from close together to far apart - making the
images seem to be grouped in pairs, with a front side always facing a front side, or a back
side always facing a back side.
In this light-ray diagram, the solid lines
show the actual path of the light rays; the
dashed lines show the path of the light rays
projected by your brain. You see images
where the dashed lines come together.
This light-ray diagram shows the rays that
come from the front of an object and those
that come from the back. After the first
reflection, you see one image in each mirror
where the dashed lines come together (1).
After the second reflection, you see a second
image in each mirror (2), and so on.
As you look at the images formed in one of
the mirrors on the diagram, notice that there
is an alternation of front and back views,
that the images appear to be grouped in
pairs, and that a front side is always facing a
front side and a back side is always facing a
back side. This corresponds to what you
actually observe in the mirrors.
An interesting variation on the version described involves gluing the two
mirrors to a block of foam rubber. Mirrors 6 x 6 inches (15 x 15 cm) work well
for this handheld portable version, but mirror size is not crucial. The foam
should separate the mirrors by about 2 to 3 inches (5 to 8 cm).
An even simpler handheld version of this Snack uses pieces of sponge as spacers, with
rubber bands holding the mirrors together. Use a soft sponge. The cheap ones used for
washing cars work well. One or two holes can be drilled into the mirror.
Squeeze the foam so that the mirrors are not quite parallel to each other. You will see a
pattern of images that curves off into infinity. Try it, you'll like it!
And if you enjoyed that one, why not take a look at the Corner Reflector Snack?