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VICKI COBB, a New York City native, received her bachelor's degree in zoology from Barnard College and her master's degree in secondary science education from Columbia University. ...
VICKI COBB, a New York City native, received her bachelor's degree in zoology from Barnard College and her master's degree in secondary science education from Columbia University. She has written many science-related books for young readers, and was the creator and host of "The Science Game," a television show. Ms. Cobb lives in Mamaroneck, New York, with her two sons.
Explains what light is and explores the basic principles of optics through experiments.
If the human race had been born blind, everything that we know about our surroundings would have had to be discovered through touching, smelling, tasting, and hearing. However, our eyes detect light. Light has been a source of information about our immediate world and has added immeasurably to our understanding of it. In addition, light has been our main source of information about the sun, planets, stars, and other heavenly bodies. Only the moon has been explored directly, and that's been in recent times. It is very human to wonder about things-like the universe-that are bigger than ourselves. It is also human to wonder about the nature of light, which brings the universe to us.
Vision, our ability to detect light, is the most dominant of our five senses. One measure of this is that we have more receptor cells in our eyes to detect light than we have receptor cells for all our other senses combined. Another is the enormous range of things we perceive, including brightness, color, contrast, depth, and motion. We are aware of light every conscious moment of our lives. So it is no surprise that many people have spent time thinking about the nature of light.
Some ideas about light go back thousands of years. In the first century A.D., a Greek engineer named Hero (20?A.D. — ?) wrote a book about mirrors and light. He believed that light was a kind of "feeler" or antenna sent out by the eyes to detect the things we saw. Hero thought that light traveled infinitely fast.
About nine hundred years later, an Arabian physicist named Alhazen (965?-1039) figured our that light comesfrom a source, such as the sun, and that everything we see reflects light from the source to our eyes. Alhazen wrote a book about light that was translated into Latin in the thirteenth century, three hundred years after he wrote it. It had a powerful influence on scientists who studied light.
Two theories arose about the nature of light. One theory said that light was a stream of partic1es that traveled in straight lines. The other said that light was made of waves. Evidence for both ideas came as scientists observed the behavior of light in their laboratories and in nature. Through experimentation they found that light can be blocked, bent, bounced, broken up, caught, filtered, and scattered. Everything we do with light reveals something about its nature. All the information we have collected about light is called the science of optics. The word "optics" comes from a Greek word (optikos) meaning "of the eye or seeing."
Any study of light begins with a source of light. The most obvious and most important source of light is the sun. Through the ages we have created other sources of light to be able to go about our business when sunlight was not available. First, there was light produced by fire. Candles and oil, and then gas lamps, illuminated people's homes for centuries. In 1879, Thomas Edison (1847-1931) introduced the first incandescent electrical lamp. An incandescent lamp uses a wire thread that is heated by an electric current until it glows. Other forms of electrical light sources are arc lamps, in which the light is a series of bright sparks, and fluorescent lamps.
The science of optics has given us the power to do some amazing things: Grocery checkout devices use a scanning laser beam to identify an item by its code, made of black bars; the checkout device then displays the price of the item on a screen. Compact disc players also use lasers to read music that has been encoded on special optical discs. Credit cards now have holograms, which are pictures with a three-dimensional appearance. Holograms are made using lasers. They are so hard to copy that they make it difficult for criminals to counterfeit credit cards. Photocopiers and fax machines use light to reproduce printed material in seconds. Light, passing through fiber-optic cables, can carry telephone calls over thousands of miles or let us peer directly inside the human body without cutting it open. We become couch potatoes as we use a form of light to change channels on our TVs without getting up. Learning about the properties of light has enabled us to see in the dark, to see through solid material, to see objects too tiny or too far away for the human eye. Light certainly will be an essential part of many great technological breakthroughs in the future.
You can experience the wonders of optics for yourself. This book shows you how. Before you begin, let us give you a few suggestions about how to use this book.
You can simply read this book from cover to cover as you would any book. Optics is presented here in a logical fashion, chapter by chapter, each topic building on ideas introduced earlier. Light is not a simple subject. For this reason, it is better not to skip around while reading this book.
The important ideas in each chapter are illustrated by experiments, which are the heart of a science like optics. The best way to use this book is to do the experiments in order as you read along.
When you do an experiment, read through the procedure and collect everything you need before you start. The procedure is the step-by-step way a scientist goes about getting information. Good procedures give clear-cut results. They also suggest other procedures for further experimentation. If you get ideas for other experiments while doing our procedures (and you probably will), keep on going. We have tried all the procedures in this book in our home laboratory and they work. But you may think of ways to improve them. Go to it! Science is the most fun when you make discoveries of your own.
Optics is an adventure worth getting your head and hands into. Once you do, the world will never look the same again. That's a promise!