READ: Light and Color

Summary

• Sunlight contains the complete range of wavelengths of electromagnetic waves. The entire range is called the electromagnetic spectrum.
• Electromagnetic waves that are commonly called light fall roughly in the middle of the electromagnetic spectrum. Light includes infrared light, visible light, and ultraviolet light.
• Infrared light is light with the longest wavelengths and lowest frequencies. You can’t see infrared light, but you can feel it as heat. Besides the sun, flames and living things give off infrared light.
• Visible light consists of a very narrow range of wavelengths that falls between infrared light and ultraviolet light. It is the only light that people can see. Different wavelengths of visible light appear as different colors.
• Ultraviolet light has shorter wavelengths and higher frequencies than visible light. Ultraviolet light also has more energy, which makes it useful for killing germs. Too much exposure to ultraviolet light can damage the skin.
• The wavelength of visible light determines the color that the light appears. Light with the longest wavelength appears red, and light with the shortest wavelength appears violet. In between are the wavelengths of all the other colors of light.
• A prism separates visible light into its different colors. As light passes through the prism, it slows and bends, but different wavelengths bend at different angles. This separates light into different wavelengths, forming a rainbow of colors.
• The wavelengths of visible light that an object reflects or transmits determine the color that the object appears to the human eye.
• The human eye can distinguish only red, green, and blue light. These three colors are the primary colors of light. All other colors of light can be created by combining the primary colors. Secondary colors of light—cyan, yellow, and magenta—form when two primary colors combine equally.
• Pigments are substances that color materials by reflecting light of certain wavelengths and absorbing light of other wavelengths. The primary pigment colors are cyan, yellow, and magenta. They can be combined to produce all other colors.

Vocabulary

• infrared light: Part of the electromagnetic spectrum in which waves have a wavelength between those of radio waves and visible light.
• ultraviolet light: Electromagnetic radiation with a wavelength falling between the wavelengths of visible light and X rays.
• visible light: Range of wavelengths of electromagnetic waves that the human eye can detect.
• pigment: Substance that colors materials by reflecting light of certain wavelengths and absorbing light of all other wavelengths.
• primary color: One of three colors of light (red, green, or blue) that can be combined to produce all other colors of light.

CK-12 Foundation, Physical Science. http://creativecommons.org/licenses/by-nc-sa/3.0/