Different colors of light have different wavelengths. Shades of purple have the shortest wavelengths, as low as 400 nanometers (or the equivalent 4,000 Ångströms). Red light has the longest wavelength, up to 700 nm (7,000 Å). Short wavelengths correspond to higher frequencies and higher energies, while longer waves oscillate at lower frequencies and carry less energy. Electromagnetic waves with wavelengths below 400 nm are in the ultraviolet (UV) portion of the electromagnetic spectrum, while waves longer than 700 nm are in the infrared (IR) region of the spectrum.
Original Windows to the Universe artwork by Randy Russell.

Light travels as waves of energy. Waves of light have different wavelengths (the distance between the top of one wave and the top of the next). Different colors of light have different wavelengths. Purple and blue light waves have short wavelengths. Red light has a longer wavelength. This picture shows the lengths of the waves of different colors of light. The longest red waves are about 700 nanometers long. The shortest purple waves are 400 nanometers long. Light waves with short wavelengths carry more energy than ones with long wavelengths. "Light" waves shorter than 400 nm are called "ultraviolet" or "UV" light. "Light" waves longer than 700 nm are called "infrared" or "IR" light. Some people use a distance unit called an Ångström to measure light waves. There are 10 Ångströms in one nanometer. Green light has a wavelength of 5,500 Ångströms, which is the same as 550 nanometers.
Original Windows to the Universe artwork by Randy Russell.

Light is made up of waves. Some waves have different sizes. The distance between the top of one wave and the top of the next wave is called the "wavelength". Different colors of light have different wavelengths. Red light has long waves. Purple light has short waves. Green light is in between. The wavelength of green light is around 550 nanometers (nm). This is the same as 5,500 Ångströms (Å). Light with short waves has more energy than light with long waves. Purple light has more energy than red light.
Original Windows to the Universe artwork by Randy Russell.

The source of this material is Windows to the Universe, at http://www.windows.ucar.edu/ at the University Corporation for Atmospheric Research (UCAR). © The Regents of the University of Michigan. All Rights Reserved. Site policies and disclaimer