NEWTON

"Visible light is something that has interested scientists for a long time. There is much that we know about light. Yet, there is a great deal that is still unknown. Few other areas of investigation are more challenging than a study of light. The unanswered questions have puzzled scientists from generation to generation. Many great scientists-Newton, Michelson, Einstein, for example-have sought answers to these questions.

Light is a form of energy. As such, it is closely related to heat and to nuclear energy. We use the energy of light to see the things around us. Light, in addition, has many practical applications in our everyday life. There are house lights, car lights, signal lights, street lights, and decorative lights. Our cameras, mirrors, microscopes, telescopes, and projectors would be useless without light. We are dependent upon light for the plants we grow and for the food we eat. We could hardly live without light.

Any luminous body can serve as a source of light. A luminous body is an object that shines by its own light. The sun is our chief source of light. It is naturally luminous. Fire, too, is luminous. A bonfire and a candle flame are luminous objects. Among other luminous objects are stars, fireflies, oil lamps, flashlights, electric lamps, and street lights.

Heat makes some things luminous. The filament in an electric-light bulb, for example, glows and gives off light because of its heat. The electrons flowing through the filament make it hot. Wherever there is light, there is usually heat. Some luminous objects, on the other hand, are relatively cool. Neon lights and fluorescent lamps do not become nearly so hot as the ordinary light bulb, or incandescent lamp.

Our knowledge of light has developed slowly over the years. Many scientists have contributed to this knowledge. To explain light and what it is, scientists have considered many hypotheses. Few areas of investigation are more exemplary of how one idea can lead to another idea. In a sense, the story of light is a story of science itselff. It is a story of observation, experimentation, theorizing, testing, retesting, and problem-solving. It is also a story of invention and discovery.

Does light consist of particles? Or is light made of waves? How fast does light travel? What is its speed? Does light have anything in common with X rays and radio waves? Can light go around objects? Or does it move only in a straight line? What makes it possible for one beam of light to pass through another beam of light?

Scientists have explored such questions as these since the days of Newton and Huygens . You, too, can investigate such problems in your study of light

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NEWTON AND THE PRISM