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When you look at every day objects, leaves during peak foliage, read a book, or help your 5 year old pick out just the right color to use on their latest masterpiece from that daunting box of 128 crayons, you are using light. You are not directly connected to the object, yet you can see the object through light that somehow left the object and reached your eyes.
Light is all our eyes can really see.
Ways of Thinking About Light
There are two ways of thinking about light: - The "particle" theory, expressed in part by the word photon
- The "wave" theory, expressed by the term light wave
Since ancient times, people have thought of light as a stream of tiny particles traveling in straight lines and bouncing off mirrors.
In the late 1600s, the idea of the light wave was presented which proposed that light acted like a wave instead of a stream of particles. In the early 1800s, physicists showed that when light passes through a very narrow opening, it can spread out, and interfere with light passing through another opening. By shining a light through a very narrow slit, we see a bright bar of light that corresponds to the slit. In addition, we can see additional light, not as bright, in the areas around the bar. If light is a stream of particles, this additional light would not be there. This experiment suggests that light spreads out like a wave. In fact, we now know that a beam of light radiates outward at all times.
Albert Einstein advanced the theory of light further in 1905. Einstein considered the photoelectric effect, in which ultraviolet light hits a surface and causes electrons to be emitted from the surface. Einstein's explanation for this was that light was made up of a stream of energy packets called photons.
Modern physicists believe that light can behave as both a particle and a wave, but they also recognize that either view is a simple explanation for something more complex. For our discussion, we will talk about light as waves, because this provides the best explanation for most of the phenomena our eyes can see.
So what is light? »
Sources include: Dictionary.com, HowStuffWorks.com
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