The Color of Opaque Bodies
المؤلف:
GEORGE A. HOADLEY
المصدر:
ESSENTIALS OF PHYSICS
الجزء والصفحة:
p-478
2025-12-21
21
under white light is determined by their relative powers of absorbing and reflecting vibrations of certain wave lengths. A body that absorbs all the colors except red, reflects that color and is red.
Demonstrations. Paste a strip of white paper upon a black card and, holding it in the sunlight, examine it by looking through a prism.
The edges of the paper will give the spectrum colors. Examine in the same way strips of red and blue paper, and the spectrum in each case will give only the color that the paper reflects.
Paste a strip of white paper, 10 in. long and in. wide, on a black card. Paste, at right angles to this, pieces in. wide and 2 in. long. Place a prism as in Fig. 1, and examine the strips. The spectra of the narrow strips into which we may suppose the long strip to be divided will overlap and give white light except at the ends, one end being red and the other violet. The spectrum of each narrow line will be a complete spectrum.
If the color that a body reflects is red, it will not appear red unless the light that shines upon it has red in it.
Demonstration. -Take slips of differently colored paper into a dark room and examine them under the light from a photographer's lamp giving a ruby red light, or under the yellow light from a candle upon which some salt has been sprinkled.
This demonstration shows the importance of selecting colors under the same light as that in which they are to be used. A color that is exactly suitable by daylight may have an entirely different appearance by gaslight.
An artificial light is better adapted for all purposes when the quality of its light approaches that of sunlight. Most artificial lights have a greater proportion of yellow in them than daylight has. The colors of the decorations used in a room should be determined in a great measure by the color of its illumination.
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