Man's physical universe

xanabras

414 ENERGY MAY BE PROPAGATED BY VIBRATIONS

tractive process. A red pigment absorbs all but the red rays, which are

reflected. A mixture of pigments of different colors reflects only those

wave lengths which neither pigment absorbs. It is a common experience

that in (the indiscriminate) mixing of pigments grays usually result,

because combinations of pigments of several colors will absorb all

of the wave lengths about equally.

The secret of the destruction of color by pigments lies in a principle

known as resonance. Resonance is illustrated by the following examples:

1. One tuning fork, when vibrating, will set up vibrations in another

tuning fork of like pitch.

2. A string in a piano will vibrate when one sings strongly the note

corresponding to a key which is gently depressed to take ofT the

damper.

3. Resonance is the foundation of radio reception. We turn the

knobs of the receiving set until the frequency of vibration in the

condensers and coils is the same as that of the wave system coming

from the broadcasting station.

Pigments absorb colors of certain wave lengths in a comparable

manner. The radio receiver absorbs long waves, while the pigment

absorbs short waves.

A study of molecular structures in relation to color gives much

information as to what part of a molecule acts as the receiver to cause

the color. Certain architectural designs of molecules result in conditions

conducive to the production of colors under proper exciting

conditions.

The Primary Colors Used in Producing Colored Lights Are Not the

Primary Colors Employed by Artists in Mixing Pigments.

The pigment primaries, reddish purple, yellow, and blue-green, are

called subtractive primaries.

A green and red light when mixed will produce a yellow sensation

by addition, but a blue-green and a purple-red pigment will produce

a bluish-gray color because nearly all

are subtracted by the two pigments.

of the colors originally present

Colored Photographs May Be Transmitted over a Telephone Wire.

Colored photographs depend upon the use of the three primary

colors, blue, red, and yellow, to produce all other colors. A colored

picture may be produced by taking three pictures of an object, using

films which are sensitive to blue,

red, and yellow colors, respectively.

These films may be combined as three different layers in one film and

may then be selectively dyed, so that the finished film will transmit a

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