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| What is Light? | Light as a Wave | Light as a Particle | Characteristics of a Photon |
| The Photoelectric Effect | The Transverse Electromagnetic Wave (TEM) |

What is Light?

Throughout human history, light has been something most of mankind has taken for granted. It is there throughout our lives for most of us, and (so we assume) will always be there in the familiar patterns we experienced as we grew up.

In the past, and in some countries even today, phenomena such as solar eclipses have been cause for great fear, because they represent a break in that familiar pattern, cutting off the light from the sun for awhile, and who could be sure if the sun would ever come back? Even in countries where an eclipse is an understood phenomenon, a solar eclipse is still an occasion for excitement and awe.

To gain any understanding of light itself, we need to step away from this mindset and examine light from a more scientific and objective viewpoint. Let's start with a dictionary definition of light, with some technical data included:


The form of radiant energy that stimulates the organs of sight, having for normal human vision wavelengths ranging from about 3900 to 7700 ångstroms and traveling at a speed of about 186,300 miles per second.

One ångstrom = 10-8 cm (0.00000001 cm).

Of course, the above definition doesn't really tell us much. Before the speed of light and its wavelength in the electromagnetic spectrum were determined, the definition would have ended at the first comma, and that really would have told us nothing about the nature of light.

So, rather than look at more definitions, let's move on to explore some of the basic properties of light as we know them today, so we can better understand not only how light will behave, but also something of why it behaves as it does. This will give us a chance to predict how light may behave under various circumstances and conditions.

Next: Light as a Wave

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