CHAPTER VII

OPTICAL ROTATION (POLARIMETRY)

Theory.-— In any ordinary beam of light the wave motion
is regarded as being transverse and in all possible pianos which
can include the axis of propagation. When such a beam pannes
through, or is reflected from, certain transparent media those
vibrations are suppressed in all but one plane. The beam of
light Ls then said to be "plane-polarized.7'

a b
FIG. 30.—-•Diagrammatic reproiwmttttion of typical piano* of vibration of («|
impoiarized and C/0 phuut-iwluriaioti tight..
This change in illustrated in Fig. 30, in which a represents norm*
of the planes of vibration of unpolarizcd light and 6 that of
plane-polarized light. In these diagrams the axis of propagation
of the beam of light is understood to be perpendicular to the
plane of the paper.
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