The fifth episode of Cosmos aired on Fox, and it is was all about the light spectrum, and how scientists from different countries (Joseph von Fraunhofer from Germany, Mozi from China, Ibn al-Haytham from Iraq, Isaac Newton from England) and time periods help us arrive at our current understanding of light. Most of the light that we see is white, and appears to have no color. However, white light is actually composed of ALL colors. When light is translated through a different medium at exactly the proper angle, the colors separate and make a rainbow. This happens with a prism, as well as with raindrops.
Interestingly enough, there is more light than in the visible spectrum. Radio waves are a form of light, as well as X-rays that you've likely seen in the hospital. Those are a few examples of other forms of light in the section beyond visible light, called the infrared spectrum.
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