Human beings have always been visual animals. For the majority of our existence, we have relied mostly on our sight to find food and shelter. And now, with the rapid development of computers, multimedia, and cyberspace, our vision is becoming increasingly more important for interaction with our immediate environment and our world. The prime vehicle of this interaction is light. We really know what light is. For most of us, it is simply what we turn on to see at night. To give us better understanding about light it is just the right time to delve a little deeper into the concept of light, to understand a little more than just that which allows us to see. We will explore how light reflects and refracts, how we can use lenses and mirrors to play tricks on nature, how color allows us to create masterpieces of art, and how nature creates her own masterpieces of light. On our journey, hopefully we will come to understand more about the role of light and optics in our universe.

Light is remarkable. Everyday, we see different kind of things, from the moment we get up in the morning until we go to sleep at night. We look at everything around us using light. We appreciate crayon drawings of a child, fine oil paintings, swirling computer graphics, gorgeous sunsets, a blue sky, shooting stars and rainbows. We rely on mirrors to make ourselves presentable, and sparkling gemstones to show affection. It would be nice if at some point in our lives we stop to think that when we see any of these things, we are not directly connected to it. We are, in fact, seeing light, light that somehow left objects far or near and reached our eyes. Light is all our eyes can really see. It is something we take for granted every day, but it is not something we stop and think about very often or even try and define. Let us take a few minutes and try and understand some things about light. Simply stated, light is the way of nature of transferring energy through space. We can complicate it by talking about interacting electric and magnetic fields, quantum mechanics, and all of that, but just remember light is energy.

Light travels very fast, but it does have a fixed velocity. In vacuum, the speed of light is 186,282 miles per second or nearly 300,000 kilometers per second, which is really like humming along. However, when we start talking about the incredible distances in astronomy, the finite nature of the velocity of light becomes readily apparent. It takes about two and a half seconds, for instance, for a radio communication traveling at the speed of light to get to the moon and back.

It is also important that we should highlight right up front that light is more generally referred to as electromagnetic radiation. Too often when we say light it is mistaken to mean optical light, which is roughly the radiation visible to our eyes. Visible light is a tiny portion of a huge smorgasbord of light called the electromagnetic spectrum. For our convenience, we break this smorgasbord up into different courses such appetizer, salad, etc. and refer to them by name, such as gamma rays, X rays, ultraviolet, optical, infrared, and radio. However, it is important to remember that they are all just light. There are no breaks and no hard boundaries in the electromagnetic spectrum just a continuous range of energy.