Chemistry Reference
In-Depth Information
TABLE 19 Refractive Index of Common
Archaeological Solids
Material
Refractive index (ρ)
Amber
1.55
Beryl
1.57-1.60
Calcite
1.48-1.66
Diamond
2.41
Ivory
1.51-1.55
Glass
Soda-lime glass
1.50-1.55
Crystal (lead glass, flint glass)
1.60-1.85
Ice
1.33
Ivory
1.54
Obsidian
1.48-1.51
Opal
1.41-1.45
Pyrite
above 1.81
Quartz
1.54-1.55
Ruby
1.76
Rutile
2.65-2.69
Sapphire
1.76-1.78
Topaz
1.60-1.65
Turquoise
1.62-1.65
Water
1.31
of the light and the wider the spread of the different-colored beams (see
Fig. 15a). The spreading of a beam of white light into beams of different
wavelengths and of different colors is known as the
dispersion of light
.
When a beam of white light passes through a transparent prism, for
example, the white light is dispersed into different colors ranging in wave-
length from about 400 nanometers (violet) to 770 nanometers (red),
known collectively as the
visible light spectrum
, shown in Figure 15b.
Most materials exhibit specific colors because they absorb certain
wavelengths (colors) from white, ordinary light. A red object exposed to
white light, for example, appears red because atoms on its surface absorb
all the other colors in the beam and reflect only red. If transparent mate-
rials contain coloring materials, such as dyes or pigments, they absorb the
characteristic color of the coloring material.
Light Scattering
When a beam of light strikes small particles in its path, the light is said to
be
scattered
: the particles send off the light incident on them in many
directions. Part of a beam incident on a translucent material, for example,
