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Ward's World+McGraw Hill - Color

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Color Thomas Weinacht, Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York. Content • Receptors • HSL color scheme Key Concepts • In the context of vision, color is the perception of different wavelengths of light. • The human visual system is able to perceive wavelengths of light between approximately 400 nanometers and 700 nanometers. • Longer wavelengths (less energetic photons) correspond to colors toward the red end of the visual spectrum, while shorter wavelengths (more energetic photons) correspond to colors toward the blue end of the visual spectrum. • Three different receptors in the human eye, known as cones, respond to three different ranges of wavelengths corresponding to blue, green, and red light. • The central wavelength of a light source is described by the term hue; the range of wavelengths (or purity) is described by saturation; and the overall intensity, or brightness, is characterized by lightness. Access to this article is being offered to Ward's World readers for free from McGraw Hill's AccessScience. An award-winning online gateway to scientific knowledge, AccessScience offers exclusive articles writing by prominent scientists, links to primary research material, videos and animations, plus faculty-designed curriculum maps for teachers. To see more content like this, learn about subscription options, and request a free trial for your school, click here. The visual perception of different wavelengths of light. Light can be understood both as electromagnetic waves and as particles called photons. Photons can have different energies. The energy of a photon determines the frequency and wavelength of the wave. The full range of wavelengths is known as the electromagnetic spectrum, which spans from the longest wavelength (lowest frequency) radio waves to the shortest wavelength (highest frequency) gamma rays. In com- mon usage, "light" refers to the small sliver of the spectrum that the human visual system is able to perceive— wavelengths between approximately 400 nanometers and 700 nanometers (1 nm = one-billionth of a meter). Each wave- length of visible light corresponds to a different color, which, in combination with other wavelengths, produces the rich palette of colors humans can distinguish (Fig. 1). A wavelength represents the distance over which a wave re- peats itself in space. Longer wavelengths of light (less energetic photons) correspond to colors toward the red end of the visual spectrum. Shorter wavelengths of light (more energetic pho- tons) correspond to colors toward the blue end of the visual spectrum (Fig. 2). The simplified set of colors usually used to describe the rainbow of the visual spectrum, from longest to shortest wavelength, is offered in the mnemonic ROY G BIV for red, orange, yellow, green, blue, indigo, and violet. Accordingly, + ward ' s science Fig. 1: A wall of colored tiles offers a small sampling of the range of colors humans can differentially perceive. (Credit: sarkelin/Shutterstock)

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