Man's physical universe

xanabras

416 ENERGY MAY BE PROPAGATED BY VIBRATIONS

orange light, and lamps are used which give orange light free from blue

light. Sodium-vapor lamps are satisfactory for this purpose. During

the daytime, the orange light of the sun is absorbed by these blue

filters, but the blue light is transmitted.

Hues, Tints, and Shades Are Color Terms Used in Art.

A hue is a color produced by one band of wave-length frequencies

of the visible spectrum. A pigment hue is a pigment which reflects

light of only one frequency or of a range of frequencies. The spectral

colors, red, orange, yellow, blue, green, indigo, and violet, are hues.

practiced eye may be able to recognize about 230 spectral hues.

A tint is obtained by adding white to a hue; for example, pink is a tint

obtained by adding white to red.

A shade is obtained by adding black to a hue or a pure color.

The relation of a hue to black or white is spoken of as value in art.

The value is said to be lighter if white is added and darker if black is

added.

The various colors of the spectrum may be arranged in the order of

their natural color value, yellow being the lightest, and blue-violet being

the darkest ;

this does not mean that black is present in the dark value or

that white is present in the light value. Thus it is seen that value has

a dual role in that it occurs in pure colors as well as in shades and tints.

Values should be close when combining colors; for example, tints or

light values are combined with neutral values as accents rather than

with black, because black is too strong a contrast. If black were wanted

as the accent, middle values would be used for the general scheme.

Values are affected by the texture of the material on which they

appear. The satin-backed crepe appears to be richer and darker on

the satin side and duller and lighter on the crepe side.

Intensity is a term used to designate the strength of a hue as compared

with gray. Intensity is a term used to refer to the purity of a

hue as contrasted with the same color to which has been added one or

more other colors; for instance, pure red is more intense than red

orange. The intensity of a hue of a given value may be decreased by

adding neutral gray. A neutral gray is one which is produced by the

admixture of complementary colors. To neutralize a color, one grays

it by adding its complement.

Colors May Also Be Produced by Interference.

The brilliant colors of the plumage of peacocks and other birds are

not due to colored pigments but to the interference phenomena which

are produced by thin transparent films on the feathers.

A

Pearls, opals,

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