CHAPTER 14POLARIZED LIGHT APPLIED TO STEREOSCOPYHE POLARIZATION OF LIGHT is one of the most interesting phe-
T nomena encountered in all optics. To go into the details of
the actual procedure would take far more space than we have
available. Moreover, many of the more beautiful of these phe-
nomena pertain to some of the more complex reactions of polar-
ized light and have no bearing upon our subject. For that reason
we shall content ourselves with a very simple explanation of the
one polarization phenomenon which has to do with stereoscopic
observation. ’
Light travels as a “ray” from the source to some given point
which may be illustrated by stretching a cord between two posts.
The cord represents the line of travel of the light. The light
itself is an electro-magnetic vibration whose direction is outwardly
from (perpendicular to) the line represented by the cord. If now
the cord is replaced by a string of Christmas tinsel, we might
assume the central core to be the line of travel and the out-thrust
tinsel strands the direction of vibration. This illustration is at
some variance from the actual theory, and wholly neglects the
projection of the wave front, but its simplicity more than out-
weighs its faults from the standpoint of advanced theory. We are
not students of advanced physics, but only trying to arrive at an
acceptable, if crude, explanation of the polarization of light,
Suppose you spray the tinsel cord with glue and then pass a
coarse comb along it with the teeth held vertically. The tinsel will
be “ironed out” and instead of a large round rope, it will be a
thin ribbon standing vertically. If you treat a similar cord with
a comb whose teeth are horizontal, you will produce another rib-
bon which lies horizontally. These ribbons now represent two
light rays which have been polarized, with their axes of polariza-
tion at go degrees. The polarized ray retains its full amplitude of
vibration only in one plane in which its own axis lies. A ray may
be polarized at any desired angle.
Now if the tinsel is allowed to dry so that it will retain its rib-
bon form against a considerable force, we can illustrate the polar-
ization phenomenon with which we are concerned.
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