Did you know that everything you see, known as visible light, is only a very small portion of the entire light spectrum? Well it's true. The lowest frequency of light that the naked eye can see is 430 trillion hertz, and the highest is 750 trillion hertz. That's a range of wavelengths from 380 nanometers to 700 nanometers. Light (electromagnetic waves) with longer wavelengths than that are called infrared and radio waves, and those with shorter wavelengths than that are called ultraviolet, x-rays, and gamma rays.
The colors of visible light are violet, blue, green, yellow, orange, and red.
In the picture above you can see that violet light has the shortest wavelength, and red has the longest. Now you may be wondering, where is white? isn't there white light? The answer to that is the color white is a combination of all the colors. This can be seen by shining a light on a prism so that the light bends and separates into the colors seen above. An example of this phenomena are rainbows. The light passes through water particles in the air and bends, revealing the spectrum of colors. Now there's only one color missing. Black. The reason black isn't part of the visible spectrum is it isn't a color at all. When something is black, that means it absorbs all the colors, so you're seeing the absence of color.
Another interesting phenomena of light again has to do with color and temperature of an object. You see, heat is a form of energy, so the hotter an object is the more energy it has. And as you learned earlier, red light has a longer wavelength and violet light has a shorter wavelength. That means red light has a lower frequency and violet light has a higher frequency. Frequency is directly related to energy, so objects that are hotter appear blue or violet, and objects that aren't as hot appear red or orange. For example, look at the picture above of the stars. The star with the lowest temperature is red, the Sun, which is hotter, appears orange/yellow, and the hottest star is blue.
Speaking of stars, the Sun is our greatest source of visible light. Even during the night, the Sun's light reflects off the moon and onto the Earth. However, you should be careful of looking at the Sun. If you stare directly at it you could seriously damage your eyes since it's so bright. And if you look at it through a telescope you'll almost definitely go blind. This is evidence that light is also a form of energy that interacts with matter, because if it weren't then it wouldn't damage your eyes.
http://www.travelization.net/
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http://missionscience.nasa.gov/ems/09_visiblelight.html
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http://www.physics.tutorvista.com/light/visible-light.html
http://www.physicsclassroom.com/class/light/u12l2a.cfm
