..... Stumper Index
Stumper #21.
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How Good Is Your Science KQ?

[i.e. your Knowledge Quotient]

- ? The Colors Of Science And Art ? -

Have you marveled at the colors of science and art: of fireworks, the rainbow, autumn colors? Do you know what makes chlorophyll green, why objects change color when they rust, or how fireflies produce colored light? How do light emitting diodes work? Why do some materials change color in response to temperature or to the application of an electric current? In what invisible ways might differently colored substances be the same?

How do we "see" color? If you shine green light in one eye and red in the other, what color will you "see"? The answer is yellow and the explanation is rather complex.

How do we "use" color? Physicians use color of tissues and bodily fluids as diagnostic aids. For thousands of years farmers have watched for pigmentation changes to indicate crop maturity.

Historical records tell us that four thousand years ago the Egyptians built healing temples of light. Patients were bathed in specific colors of light to produce specific effects. How much credibility should we ascribe to such reports? Can a person experience different physiological reactions under different colored lights?

How do we "make" color? From ancient times cloth makers have colored their fabrics using natural dyes made from crushed plants, shellfish, beetles, or metallic ores. As long ago as the Stone Age, artists creating cave paintings used paints with brown, red and yellow pigments made from earths containing iron oxides.

We live in a fascinatingly colorful world where scientists and artists find color revealing, intriguing, expressive and wondrous. The artist Vincent Van Gogh wrote to his younger brother Theo, "One has to put very little yellow into a color to make it seem very yellow if one puts that color in or next to a violet or a lilac tone."

Van Gogh, painting in the mid to late 1800s, used oil paints containing such pigments as red ochre, chrome yellow, zinc white, and cobalt blue.

a) Which of these paints would have contained iron oxide?
b) Which would have reflected light with a wavelength of 560 nanometres?

...[RAH]...

NOTES:
(i) The picture at upper right is copyright 1992 by Richard Megna - used with permission. For information about the chemistry displayed in the photo, click on the image.
(ii) The picture at the lower right is a small piece of Van Gogh's 1888 painting "Outdoor Cafe at Night."

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