a. Wavelengths in the region of light are measured in millimicrons. These units
are also shown along the bottom of the spectrum in the illustration. Visible light
is made alp of that portion of the spectrum between 380 and 780 nanometers (fig 1-
2). The usable portion of the light spectrum for television falls between 400 and
700 nanometers (fig 1-3).
Visible light spectrum
Visible light spectrum used for color television
b. When all of the light spectrum from 400 to 700 nanometers is presented to the
eye in nearly equal proportions, white light is seen. This white light is made up
of various wavelengths which represent different colors.
Passing light through a
prism will show the composition of the visible light spectrum, (fig 1-4).
light spectrum is broken up into various wavelengths, with each wavelength
representing a different color.
The ability to disperse the light with a prism
results because light with shorter wavelengths travels slower through glass than
does light of longer wavelengths.
Six distinct colors are visible when passing
white light through a prism. Since the colors of the spectrum pass gradually from
one to the other, the theoretical number of colors becomes infinite. It has been
determined that about 125 colors can be identified in the visible spectrum.