A brief HistoryThe visible light spectrum was first observed and named by Isaac Newton, who lived in the 17th century. He used a prism to project a blurry image on his wall. He thought that the image looked ghost-like, so he made up the word "spectrum," which comes from the Latin word for ghost, "specter".RainbowsHave you ever wondered why sunlight going through a prism comes out the other side broken up into colors? Each color of light has a different wavelength. Blue wavelengths, for example, are shorter than red wavelengths. In sunlight, all the wavelengths (colors) are mixed together, and they travel at the same speed (186,000 miles a second!). When light passes through glass (or sometimes raindrops), it changes its speed just a little. But each wavelength, which makes up the light, changes its speed by a different amount! (The reason is that short blue wavelengths interact with the glass in the prism a little differently than longer, red wavelengths do.) The differences in speed cause each wavelength to bend a little differently when the light comes out the other side of the prism. Bluer wavelengths get bent more than red wavelengths, and so the sunlight gets spread out into its different colors! |
