Callister - An introduction - 8th edition

842 • Chapter 21 / Optical Properties
Figure 21.1 An
electromagnetic
wave showing
electric field e and
magnetic field H
components, and the
wavelength .
Position
H
For a vacuum,
dependence of the
velocity of light on
electric permittivity
and magnetic
permeability
determined by wavelength; for example, radiation having a wavelength of approximately
0.4 m appears violet, whereas green and red occur at about 0.5 and 0.65
m, respectively. The spectral ranges for the several colors are included in Figure
21.2. White light is simply a mixture of all colors. The ensuing discussion is concerned
primarily with this visible radiation, by definition the only radiation to which
the eye is sensitive.
All electromagnetic radiation traverses a vacuum at the same velocity, that of
light—namely, 3 10 8 m/s (186,000 miles/s). This velocity, c, is related to the electric
permittivity of a vacuum 0 and the magnetic permeability of a vacuum m 0 through
c 1
(21.1)
2 0 m 0
Thus, there is an association between the electromagnetic constant c and these electrical
and magnetic constants.
Figure 21.2 The
spectrum of
electromagnetic
radiation, including
wavelength ranges
for the various
colors in the visible
spectrum.
Energy (eV) Wavelength (m)
Frequency (Hz)
10 8
10 22 10 –14
10 –10 10 4 10 4
-Rays 10 6
10 20 10 –12
X-Rays 10 4
1 angstrom (Å)
10 18 10 –10
1 nanometer (nm)
Ultraviolet
10 2
10 16 10 –8
–Visible
10 0
10 14 10 –6 1 micrometer (m)
Infrared
10 –2
10 12 10 –4
1 millimeter (mm)
Microwave
10 –4
10 10 10 –2
10 –6
10 8 10 0 1 meter (m)
Radio, TV
10 –8
10 6 10 2
1 kilometer (km)
Visible spectrum
wavelength
0.4 m
0.5 m
0.6 m
0.7 m
Violet
Blue
Green
Yellow
Orange
Red