Section V. COLOR

TM 9-258

c. Image Size.

An observer receives the

magnification produced by a simple magnifier. It is

useful in some camera viewfinders, but since it does not

impression that the image seen on the other side of the

magnify or produce a real image its usefulness is limited

lens is smaller than the object. This effect is known as

in military instruments.

reduction as contrasted with

Section V. COLOR

through a triangular cross-section glass prism, the

2-26.

General.

emergent light is split into a number of refracted rays. If

these refracted rays are made to fall upon a screen, they

a. Ordinary sunlight or any other "white" light is a

produce a band of colored light called the solar

mixture of visible light of all wavelengths. "White" light,

spectrum. The colors of the spectrum are, on order; red,

is, therefore, a mixture of all colors.

orange, yellow, green, blue, indigo, and violet. About

b. The amount of deviation of light from its path

130 distinct hues have been observed.

depends upon the color of the light as well as upon the

b. Each color of the spectrum represents light

shape and optical density of the optical element. Each

vibrating at a different frequency or wavelength. The

color of light has its own distinctive wavelength and there

shorter the wavelength, the more the rays are bent upon

is a different index of refraction for each color. The

being refracted. Red light has the longest wavelength

unequal deviation of rays of light of various colors,

(A, fig 2-51); violet, the shortest. Red rays are bent the

dispersion as it is called, has an important effect on the

least; violet, the most; the rays of other colors are

formation of images, and, therefore, upon the design of

interspaced accordingly

fire-control instruments.

2-27. Separation of "White" Light.

a. If sunlight is passed through a slit and then

2-37