PHYSICS 111 LASER AND LIGHT
INTRODUCTION
Light exists all over the empty space in the universe. It dwells in the deepest darkness of the night sky and in the farthest reaches of space. It is so common to us that we are unaware of its presence. Looking at the myriad of stars in a dark night amazes a person. We suspect the prehistoric people were the first to ignite fire to cook their food and to warm their bodies in winter. There is clear evidence from the ruins of the ancient civilizations that, sun was considered god because of its tremendous light emitting power. The greatest light detector of all, is the human eye. Even today, the vision of eye is not fully understood.
Light is that entity which, permits vision with the help of eye. Light is a form of energy. We do not see light, but perceive objects constructed by brain about their shape, color, texture and the state of motion. Sources of light are hot bodies, lightning, electric discharges, insects, and fire. Light stimulates vision. So much for the definition, frankly speaking nobody found the truth about light. Did you?
Our course is geared towards a bird's eye view of physicist's light. In a different view, light is considered knowledge (sometimes-spiritual knowledge) in a metaphorical sense as in literature or religion (not a favorite topic of many scientists). You should realize that you will begin a course about Light which pervades such diverse subjects as physics, astronomy, chemistry, mathematics, theology, psychology, biology and medicine. Isn't it exciting to study it?
WONDERS OF LIGHT
1. Light is the most ancient object of all things created. Mentioned in the Bible in its beginning verses, started on the eve of creation of the universe which physicists believe, credit goes to Einstein who gave us a working principle in his Big Bang Theory of the Universe.
2. The oldest object reaching the earth is light, which may have started its journey at a distant star in a galaxy billions of years ago.
3. When light moves, it moves with the greatest speed of all things, its speed is 186,000 miles per second. When it stops, it no longer exists. We say it is absorbed.
4. It has all the colors for the beauty.
5. Its mass called rest mass is zero unlike any other thing.
6. Our most sophisticated knowledge of physics, tells us that light can be a particle or a wave.
7. It is a physical quantity; nobody has ever explicitly seen it.
8. It is extremely tiny. Its dimension called wavelength, is about a thousand part of a millimeter.
9. It has Energy and Momentum with their characteristic unusual values.
10. Many simple applications of quantum mechanics are in light.
11. Light emitted by a laser, is one of the most fascinating inventions of our time.
12. All the knowledge of Einstein's Relativity is based on the critical speed of light.