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science f o u n dat i o n s Light and Sound SCIENCE FOUNDATIONS The Big Bang Evolution The Genetic Code Germ Theory Gravity Heredity Light and Sound Natural Selection Planetary Motion Plate Tectonics Radioactivity Vaccines science f o u n d at i o n s Light and Sound P. Andrew Karam and Ben P. Stein Science Foundations: Light and Sound Copyright © 2011 by Infobase Publishing All rights reserved. No part of this book may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage or retrieval systems, without permission in writing from the publisher. For information, contact: Chelsea House An imprint of Infobase Publishing 132 West 31st Street New York, NY 10001 Library of Congress Cataloging-in-Publication Data Karam, P. Andrew. Light and sound / P. Andrew Karam and Ben P. Stein. p. cm. — (Science foundations) Includes bibliographical references and index. ISBN 978-1-60413-344-8 (hardcover) ISBN 978-1-4381-3522-9 (e-book) 1. Light—Popular works. 2. Sound—Popular works. I. Stein, Ben P. II. Title. III. Series. QC358.5.K37 2010 535—dc22 2010015736 Chelsea House books are available at special discounts when purchased in bulk quantities for businesses, associations, institutions, or sales promotions. Please call our Special Sales Department in New York at (212) 967-8800 or (800) 322-8755. You can find Chelsea House on the World Wide Web at http://www.chelseahouse.com Text design by Kerry Casey Cover design by Takeshi Takahashi Composition by EJB Publishing Services Cover printed by Bang Printing, Brainerd, MN Book printed and bound by Bang Printing, Brainerd, MN Date printed: October 2010 Printed in the United States of America 10 9 8 7 6 5 4 3 2 1 This book is printed on acid-free paper. All links and Web addresses were checked and verified to be correct at the time of publication. Because of the dynamic nature of the Web, some addresses and links may have changed since publication and may no longer be valid. 1 What Waves Are 2 What Light Is and How It Can Be Used 19 3 What Sound Is and How It Can Be Used 39 4 Light and Sound and the Senses 56 5 Extending the Senses 69 6 Light and Sound in the Universe 87 7 Glossary 96 Bibliography 100 Further Resources 101 Picture Credits 103 Index 104 About the Authors 109 What Waves Are T he universe began with a burst of light—on this fact, both scientists and many religious leaders agree. Since the universe’s birth, it has been permeated by photons—particles of light. Some of them are visible to human eyes, but most of them are invisible. The universe radiates photons in a spectrum from low-energy radio waves to highenergy gamma rays, with visible light somewhere in between. The early universe also rang like a very low-pitched bell, and astronomers are only now beginning to learn how to study these cosmic sounds and use them to learn more about the earliest moments of creation. Sound and light are part of everyday life. People gather most of their information about their surroundings through the light that enters their eyes and the sounds that enter their ears. They see reflections in a mirror, the faces of loved ones, and rainbows after a storm. They hear music, voices, and the din of traffic. People put sound to work, too: They use ultrasound to peer inside the body, as well as to clean teeth and jewelry, while elephants and whales use low-frequency sound (infrasound) to communicate over long distances. In addit