In this interactive activity adapted from Shedding Light on Science, learn about the primary colors of light and pigment. First, see red, green, and blue gelatin blocks used as filters to demonstrate the absorption of specific wavelengths of light. Then watch as three desk lamps with red, green, and blue filters show how the primary colors of light are mixed to create other colors. Finally, watch a demonstration of how paints both absorb and reflect light and how the primary colors of pigment are mixed to create other colors.
The inner surfaces of your eyes contain photoreceptors—specialized cells that are sensitive to light and relay messages to your brain. There are two types of photoreceptors: cones (which are sensitive to color) and rods (which are more sensitive to intensity). You are able to "see" an object when light from the object enters your eyes and strikes these photoreceptors.
Some objects are luminous and give off their own light; all other objects can only be seen if they reflect light into your eyes. However, humans can only see visible light, a narrow band of the electromagnetic spectrum (which also includes non-visible radio waves, infrared light, ultraviolet light, X-rays, and gamma rays). In terms of wavelengths, visible light ranges from about 400 nm to 700 nm.
Different wavelengths of light are perceived as different colors. For example, light with a wavelength of about 400 nm is seen as violet, and light with a wavelength of about 700 nm is seen as red. However, it is not typical to see light of a single wavelength. You are able to perceive all colors because there are three sets of cones in your eyes—one set that is most sensitive to red light, another that is most sensitive to green light, and a third that is most sensitive to blue light.
Red, green, and blue are the primary colors of light—they can be combined in different proportions to make all other colors. For example, red light and green light added together are seen as yellow light. This additive color system is used by light sources, such as televisions and computer monitors, to create a wide range of colors. When different proportions of red, green, and blue light enter your eye, your brain is able to interpret the different combinations as different colors.
However, there is another set of primary colors with which you may be more familiar. The primary colors of pigment (also known as subtractive primaries) are used when producing colors from reflected light; for example, when mixing paint or using a color printer. The primary colors of pigment are magenta, yellow, and cyan (commonly simplified as red, yellow, and blue).
Pigments are chemicals that absorb selective wavelengths—they prevent certain wavelengths of light from being transmitted or reflected. Because paints contain pigments, when white light (which is composed of red, green, and blue light) shines on colored paint, only some of the wavelengths of light are reflected. For example, cyan paint absorbs red light but reflects blue and green light; yellow paint absorbs blue light but reflects red and green light. If cyan paint is mixed with yellow paint, you see green paint because both red and blue light are absorbed and only green light is reflected.
Academic standards correlations on Teachers' Domain use the Achievement Standards Network (ASN) database of state and national standards, provided to NSDL projects courtesy of JES & Co.
We assign reference terms to each statement within a standards document and to each media resource, and correlations are based upon matches of these terms for a given grade band. If a particular standards document of interest to you is not displayed yet, it most likely has not yet been processed by ASN or by Teachers' Domain. We will be adding social studies and arts correlations over the coming year, and also will be increasing the specificity of alignment.