Visible light For eons the visible spectrum was the key to learning about the universe. What we refer to as white light is really the combination of all colors of light. Each color of light has a specific wavelength. Red has the longest wavelength and violet has the shortest. When these wavelengths travel through one type of medium (air) and then enter and travel through another type of medium (water) they are bent or refracted. The longer the wavelength, the less the refraction. If you recall looking at a rainbow, you will always see a specfic order of colors in that spectrum. This order will always be red, orange, yellow, green, blue, and violet (ROYGBV). The red color has been bent (refracted) the least amount, whereas the violet color, the greater amount. However the visible spectrum ( which is the part of the spectrum ( NASA movie) to which our eyes respond) is just a small piece of the electromagnetic spectrum. Although the sun is a major source of light, there are many others in the universe. In studying these various sources with special instruments we can learn much more than what our eyes can tell us. One of these special types of instruments is a spectroscope. It separates the light coming from a source (such as the sun/star/street lamp) into its compomnent colors. The spectras produced by this instrument allow the astronomer to determine the chemical make up of the star's outer layer, temperature, pressures, magnetic fields, etc. It also is used in determining whether the star or other light source is moving towards or away from the earth (doppler effect). There are three types of spectras produced. They are continuous, absorption, and bright-line spectras. Each type gives clues to its light source.
|