Pub. date: 2010 | Online Pub. Date: December 16, 2009 | DOI: 10.4135/9781412972000 | Print ISBN: 9781412940818 | Online ISBN: 9781412972000| Publisher:SAGE Publications, Inc.About this encyclopedia
Differently colored lights can be mixed together optically to produce lights of another color. Which lights and which mixtures perceptually match each other can be predicted from a few relatively simple rules. The simplicity of these rules, discussed in this entry, derives from the properties of the visual photoreceptors in our eyes that convert arriving photons into neural signals, rather than from physics. The visible spectrum is that part of the electromagnetic spectrum that we can see. It covers wavelengths from about 390 to 730 nanometers (nm). When viewed alone, the appearance of monochromatic lights made up of single wavelengths varies across the spectrum from violet at short wavelengths through blue, blue-green or cyan, green, yellow-green, yellow, orange to red at long wavelengths. Sodium street lighting, which appears yellow, is a commonly encountered example of lights that are nearly monochromatic. Most lights that we encounter in the natural environment broadband ...