[Shown.]
(5) The spectrum of the reflected light is frequently found to
consist almost entirely of a comparatively narrow band. When the
angle of incidence is increased, the band moves in the direction
of increasing refrangibility, and at the same time increases
rapidly in width. In many cases the reflection appears to be
almost total.
[Illustration: FIG. 1 GENERAL SCHEME
FIG. 2 DETAIL OF LAZY-TONGS]
In order to project these phenomena a crystal is prepared by cementing
a smooth face to a strip of glass whose sides are not quite parallel.
The white reflection from the anterior face of the glass can then be
separated from the real subject of the experiment.
A very remarkable feature in the reflected light remains to be
noticed. If the angle of incidence be small, and if the incident light
be polarized in or perpendicularly to the plane of incidence, the
reflected light is polarized in the _opposite_ manner. [Shown.]
Similar phenomena, except that the reflection is white, are exhibited
by crystals prepared in a manner described by Madan. If the crystal be
heated beyond a certain point the peculiar reflection disappears, but
returns upon cooling. [Shown.]
In all these cases there can be little doubt that the reflection takes
place at twin surfaces, the theory of such reflection (_Phil.
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