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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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