Introduction

Light and Optical Systems

The sense of sight is extremely important to us, as it provides us with a large part of our information about our world. We are all familiar with light - or think we are. Our eyes respond to the light we receive from objects all around us. Right now you are receiving light from the computer screen you are looking at and in the illustration below you are likely seeing various shades of red, yellow, green and blue against a black background.

How do we see?

What is the something called light that enters our eye and causes the sensation of light?

How does light behave so that we can see the great range of phenomena that we do?


The subject of light will occupy us for this unit.

We see objects in two ways:

The object may be a source of light such as a light bulb, a flame or a star, in which case we see the light emitted directly from the source. The illustration is an example of stars as captured by the Hubble telescope.
More commonly, we see an object because of the light reflected from it. In this case, the delicate pastel shades of this pottery reach our eye only when light from another source is reflected from the pots.
Optical devices improve and extend our vision. Tools such as the telescope and the microscope have helped us extend our knowledge in a variety of fields from the study of cells to the study the universe.

One of the ways we learn about the nature of light and its behavior is thorough the use of geometric ray models. The illustration is a representation of the reflection of light from a flat surface. This is the experimental side of the study of light and its properties.

Welcome to the wonderful world of light!

© 2002 Alberta Online Consortium

Lesson 1

Lesson 1: Challenges
Science in Action 8
Read pages 176 - 181 and make notes in your notebook.




Light is all around us and certainly something that we know about - or do we? How does light make it possible for us to see things? Why can we not see around corners? Why do we see nothing in a completely dark room?


These questions and many others about the nature of light have haunted humans for centuries. In this section, we will examine the thinking of some great scientific thinkers of the past. Then we will take a look at some of the properties of light.

Some of the earliest recorded studies of the nature of light dates back to the times of the ancient Greeks - somewhere in the sixth century B.C. Lets examine the thinking of some prominent scientists: Pythagoras (from ancient Greek times) thought that light was actually beams that came from a person's eyes. When these beams reached an object, the person would see it. The trouble with his theory was that we cannot see in a completely dark room even though our eyes are open. Aristotle (another ancient Greek) thought that light consisted of waves that came from a light source and graveled to the eye. He thought that these waves moved like ripples on water. The seventeenth century A.D. was a very productive time for scientists examining the nature of light. Many discoveries were made on how light travels and how fast it travels.


Newton ( an English scientist) thought that light was a stream of particles that moved from a light source to objects. He worked with prisms to show that white light could be split into all the colors of the rainbow. More interestingly, a second prism could turn all these colors back into white light again. He thought that light of different colors had different amounts of energy. Blue light has more energy than red light, but it has a shorter wavelength.


Huygens (a Dutch scientist) agreed with Aristotle and thought that light moved as waves.

Roemer (a Danish scientist) determined the speed of light using a telescope and the moons of Jupiter. His measurements were quite accurate and showed that all light travels at one speed.

Michelson (an American scientist) confirmed Roemers findings of the speed of light using two findings between tow mountains in California.

Read very carefully the pages assigned in your text to understand some of the properties of light. Your readings will give you evidence for the properties of light summarized below:



1. Light is a form of energy.

2. Light travels in straight lines

3. Light travels at a fixed speed.

Here is a neat web site that discusses some of the properties of light. 


http://www.opticalres.com/optics_for_kids/kidoptx_p1.html