TC 9-64 _________________________________________________________________________
Figure 1-18. Use of a Prism to Split White Light into Different Colors
1-91. When a beam of white light (sunlight) is passed through a prism, as
shown in figure 1-18, it is refracted and broken down into its component
wavelengths. (This phenomenon of breaking light down into its component
wavelengths is known as dispersion.) Each of these wavelengths causes a
different reaction of the eye, which sees the various colors that compose the
visible spectrum. The visible spectrum is recorded as a mixture of red,
orange, yellow, green, blue, indigo, and violet. White light results when the
primaries (red, green, and blue) are mixed together in overlapping beams of
light. (These are not the primary colors used in mixing pigments, such as in
paint.) Furthermore, the complementary or secondary colors (magenta,
yellow, and cyan) may be shown with equal ease by mixing any two of the
primary colors in overlapping beams of light. Thus, red and green light mixed
in equal intensities make yellow light; green and blue produce cyan (blue-
green light); and blue and red correctly mixed produce magenta (a purplish
red light).
LIGHT AND COLOR
1-92. All objects absorb some of the light that falls on them. An object
appears to be a certain color because it absorbs all of the light waves except
those whose frequency corresponds to that particular color. Those waves are
reflected from the surface, strike your eye, and cause you to see the particular
color. The color of an object therefore depends on the frequency of the
electromagnetic wave reflected.
LUMINOUS BODIES
1-93. If an object is the source of light energy, it is called luminous. If the
object is not the source of light but reflects light, it is called an illuminated
body.
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