Here’s a polished transcription:

Light, Color, Waves, and Sound: An Introduction

In the mysterious writings of the ancient prophet Daniel, you can read his prediction of an extraordinary new age that would arrive far into the future, when “many will travel to and fro, and knowledge will vastly increase.” Daniel wrote these words at a time when travel was rare, the camel was the fastest means of transport, oxen plowed the fields, and men labored from dawn to dusk to make a living—over 2,000 years ago in the mighty kingdom of Babylon.

We live in that age, foretold by Daniel—the age of technology, electronics, and nuclear power, an age when knowledge has indeed exploded. Today, there are more scientists and engineers alive than have ever lived in all of history put together. People travel to and fro in fast cars and supersonic aircraft, and world travel and communication have shrunk the planet into a global village. We now possess the awesome power to destroy all life on Earth, leaving it as a blackened ball silently spinning in space.

This book is designed to help you understand the fundamental laws of science that have made such amazing progress possible and to show how technology exploits these laws to improve the quality and comfort of our lives. The reading sections explain the important ideas. Study them carefully, reading them over two or three times if necessary, and make sure you understand them. If anything is unclear, make a note of it and discuss it later with your teacher. Pay special attention to the sections printed in italics.

Nobody else can learn for you, just as nobody else can build your muscles or make you fit. So, get fully involved in the practical activities and develop your skills. Do not let yourself become a mere spectator. The analysis items will test your understanding of the practical work. In the question sections, the first items will test your recall and basic understanding of the ideas studied. This will usually lead to an analysis of useful devices or everyday applications of science. The starred questions are intended to be more challenging—ask your teacher if you get stuck.

Educated people know how to use resource books to find information for themselves. For this reason, you will find library items that allow you to develop your research skills. Your teacher may then give you the chance to develop your speaking skills by reporting your findings back to the class. The greatest resource of any nation is not coal, oil, or even gold deposits; it is the creative power of its people, and creativity can be developed by practice. Therefore, there are two other types of questions. Investigation items require you to design your own experiments, which may then be carried out in the lab. Design items ask you to solve a problem by inventing and designing.

Now, we begin the first section on page five for those keeping track at home. By the way, this is ISBN 0-721787-8, and we’re on page five.

Contents
1. Light (Page 5)

A simple definition of light is that it is what makes things visible. We see things only because they reflect light to our eyes or because they produce their own light. Luminous objects, such as the sun, produce their own light; most objects are non-luminous and do not. So, strange as it sounds, we would actually be invisible if there were no light to reflect off of us. Without light, nothing would be visible, and life would be exceedingly difficult—an understatement. No wonder knowledge is often compared to light.

The ancient Greeks were interested in light. Pythagoras taught that some kind of ray shot out of the eye and bounced back when objects were looked at. Today, we believe that light simply enters the eye for vision, with nothing emitted from it. The Greeks knew that light traveled in straight lines and that in reflection, the angle of reflection was equal to the angle of incidence—the angle at which the light hits a mirror.

The ancient Babylonians performed eye operations and discovered the small convex lens in the eye. They removed lenses made opaque by growths called cataracts. Lenses were made from transparent minerals and semi-precious stones, then later ground out of glass blocks. The word “lens” comes from the name “lentil,” because the lens resembles the shape of a lentil seed.

Around A.D. 150, Ptolemy wrote a five-volume work on optics, the study of light. He knew that a ray of light was bent or refracted when it passed from air into water. He also understood that light from a star bent as it entered the Earth’s atmosphere, causing a star near the horizon to appear higher in the sky than it actually is. The sun is affected similarly. However, Ptolemy still believed that light rays started in the eye or that something left the eye and joined with the light for the return journey.

By the Middle Ages, lenses were in common use. It was found that older people could read better with a magnifying convex lens. The next step was to mount the lenses in frames to make spectacles. This was done during the time of Roger Bacon, around A.D. 1286. In his book Opus Majus, Bacon used ray diagrams to explain the action of a convex lens.

In 1604, Kepler correctly explained that long- and short-sightedness was due to the eye lens not focusing rays on the retina properly. As early as 1675, Ole Rømer was able to estimate the speed of light from observations of Jupiter’s satellites and achieved a value about 75% accurate. However, Galileo insisted that light traveled instantaneously because he could not measure the time it took for light to reflect back from a distant mirror. Rømer succeeded because he used very large distances in space.

Today, we know that light in a vacuum travels at 300 million meters per second, or 186,000 miles per second—one million times the speed of sound. The distances in space are so vast that they are measured in light-years, the distance light travels in one year. Even with these incredibly large units, the nearest star to the Sun, Alpha Centauri, is 4.3 light-years away. This means that when we look at this star, we are seeing light that began its journey 4.3 years ago. There are objects in the universe thousands of light-years away.

Thank you, J.A. Thomas. Alright, I’ll pause here, and then we’ll move on to the questions.