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DISPERSION & PRISMS
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DISPERSION
Visible light, also known as white light, consists of a
collection of component colors. These colors are
often observed as light passes through a triangular
prism. Upon passage through the prism, the white
light is separated into its component colors - red,orange, yellow, green, blue and violet. The
separation of visible light into its different colors is
known as dispersion.
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each color is characteristic of a distinct wave
frequency; and different frequencies of light waves
will bend varying amounts upon passage through a
prism. In this unit, we will investigate the dispersion
of light in more detail, pondering the reasons whydifferent frequencies of light bend or refract different
amounts when passing through the prism.
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The rays that emerge spread out in a series of
colors known as the visible spectrum. These
colors, in order of decreasing wavelength, are red,
orange, yellow, green, blue, and violet. Clearly, the
angle of deviation 3 depends on wavelength. Violetlight deviates the most, red the least, and the
remaining colors in the visible spectrum fall
between these extremes. Newton showed that each
color has a particular angle of deviation and that thecolors can be recombined to form the original white
light.
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The dispersion of light into a spectrum is
demonstrated most vividly in nature by the
formation of a rainbow, which is often seen by an
observer positioned between the Sun and a rain
shower.
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TOTAL INTERNAL REFLECTION
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TOTAL INTERNAL REFLECTION
An interesting effect called total internal reflection
can occur when light is directed from a medium
having a given index of refraction toward one
having a lower index of refraction.
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OPTICAL FIBERS
A interesting application of total internal reflection is the use
of glass or transparent plastic rods to “pipe” light from one
place to another. As indicated in Figure 35.29, light is
confined to traveling within a rod, even around curves, as
the result of successive total internal reflections. Such alight pipe is flexible if thin fibers are used rather than thick
rods. A flexible light pipe is called an optical fiber. If a
bundle of parallel fibers is used to construct an optical
transmission line, images can be transferred from one point
to another. This technique is used in a sizable industryknown as f iber opt ics .
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