Light and Color

First Things First...
Before the topics of light and color can be explored, there must first be an understanding of waves. Waves have high and low points, and the distance between one of those highs and lows and the next is called a wavelength. Just how long that wave is will determine the amount of energy that it has. For example, a long wave has a low amount of energy or low frequency, and a short wave has a high amount of energy or high frequency. What we see in a rainbow, then, are the wavelengths of the visible colors. You see, our sun emits its radiation in this visible range, which our eyes interpret as the colors of the rainbow. These colors are identified as the visible spectrum and are often times remembered as ROY G. BIV: red, orange, yellow, green, blue, indigo, and violet.

Wave Travel
It sounds logical so far, but how are these waves related to light and color? Light travels in the form of a wave. It is basically photons (pieces of energy or particles), and mostly moves as waves. White light, or the light from the sun, is made of colors, and colors are different types of light recognized by their own wavelengths. Waves exist above and below the visible spectrum, too. Such waves called radio, microwave, and infrared are below the red end of the spectrum, and ultraviolet (UV), x-rays, and gamma rays are above the violet. These cannot be seen by the human eye, and therefore constitute the "invisible" spectrum. Together, the visible and invisible spectrums make up the electromagnetic spectrum.

Light Transfer
There are three things that can happen to a light wave. It can be reflected, absorbed, or transmitted. This is determined by the object that the wave hits, and that will give it its color. For an object to be black, it means that all the wavelengths of light hitting that object are absorbed; no light is reflected. Solid objects, for the most part, will reflect light, and transparent objects will transmit light through them. To illustrate this last fact, place a glass of red fruit juice on a table. Hold a piece of white paper on one side of the glass and chances are, if the light in the room is right, you will see red on that piece of paper. The light transmitted the red color of the juice onto the paper.

Color from Light
The color of anything depends on the type of light sent to our eyes; light is necessary if we are to have any perception of color at all. An object is "colored," as stated above, because of the light it reflects—all other colors are absorbed into that specific object. So then, an apple appears red because it reflects red light.

White light from the sun contains all the possible color variations. Yet, the human eye can only respond to certain colors and wavelengths, and not everyone sees the same colors or exact same shades of a color. We are capable of seeing color because our eyes have light and color-sensitive receptors. These receptors are called rods (receptive to amounts of light) and cones (sensitive to colors). Being able to see color is a sensation, just like smelling a pie fresh out of the oven or tasting your favorite meal. Different foods smell and taste different to each person, and likewise, no color is seen exactly the same by two people, because each person's rods and cones vary.

Pigment Color
An artist's traditional color wheel has 12 colors: 3 primary, 3 secondary, and 6 tertiary. Some materials let certain colors pass through them, and absorb other colors. These materials are called dyes or pigments. The primary colors of pigment are red, blue, and yellow. Mixing these primary colors of pigment gives us the three secondary colors: red+blue=violet, red+yellow=orange, and yellow+blue=green. Then, the primary colors mixed with the secondary give us the tertiary. They are: red- violet, red-orange, yellow-orange, yellow-green, blue-green, and blue-violet.

Light Color
The primary colors of light are red, blue, and green, and the secondary are yellow, cyan, and magenta. It is very important to know that mixing pigment and mixing light are very different. Red and green paint, for example, make brown paint, but red and green light make yellow light. When beams of light are mixed without any absorption, an additive process occurs. The more we mix the beams, the closer they get to being white light. However, when we put light through a color filter, a subtractive process occurs. Some wavelengths of light are being absorbed (subtracted) and we only see the wavelengths that are selectively given off. The Additive and Subtractive Models are explained further below.

Additive Color
As stated previously, the primary colors of light are red, blue, and green. These occur in the Additive Color (RGB) Model, so named because black is the base and light is "added" to eventually get to white, which is all of the colors together. Additive colors are seen in televisions, nature, and the computer screen you are looking at right now. Amazingly enough, colors are perceived in our eyes and brains by a three-color code; three different particles in the retina are sensitive to—you guessed it—red, blue, and green. Just as any color of the spectrum can be made by mixing the three primary colors, so do our own eyes discern the various colors by sensing different wavelengths with these three receptors.

Subtractive Color
The Subtractive Color (CMYK or CMY) Model is used for printed publications. There are only four colors that offset the printing process. The subtractive colors are also the secondary colors in light: cyan, magenta, and yellow. Black is used in the subtractive model as well, because cyan, magenta, and yellow make more of a dark gray than pure black when they are combined. In the Subtractive model, light reflected off a surface is what the surface doesn't absorb.

The Color Factor
The impact that a color has depends on a combination of three factors: hue, saturation, and luminance. Hue simply means the actual shade or color, saturation is just how pure the hue is, and luminance is what is described when we say that a color is either light or dark.

Color Complements
Complementing colors also have to be considered if you are seriously pondering color combinations. They highly contrast each other, and when placed side by side, enhance the color of the other. Color complements are on opposite ends of the color wheel; they also happen to have drastically different wavelengths.

"Shadowing" Light and Color
All of us have the potential to see light and colors "in a different light," so to say—even if we aren't color blind. Trace a ray of light from a point on a solid object to a light source. If the ray of light hits another object before you get to the light source, the point is in shadow. A shadow, present in an area where there is less light, must be opposite a light source. The light, object, and shadow will all be in a line. This is because light moves in straight lines. Shadows are caused by objects blocking light from a bright source. Materials may block some (translucent), all (opaque), or none (transparent) of the light hitting them. We can see that shadow influences the light that we are able to see, but we should also know now that this means the colors of objects will be altered as well. Since color depends on the light that we see, if some, all, or none of that light is blocked, some, all, or none of the colors will be changed. Shading makes colors appear darker, since the luminance (darkness or lightness) is altered. Since the sun's light contains all the color possibilities, changed light will change colors as well.

Coloring Vision, Appetite, and Mood
If you think colors are pretty to look at but have no real impact on people, think again. Certain colors are known to have definite behavior-altering capabilities. Some colors or combinations of them irritate eyes and cause headaches. For example, bright yellows—either on walls or as the background on a computer screen—are the most bothersome colors and are not calming or relaxing in any way. Bright colors reflect more light, so yellow over-stimulates our eyes, causing strain and even irritability. You wouldn't ever want to paint a baby's room yellow, but you could certainly use it on important street signs to attract attention.

Other colors can alter how or what we eat. Blue is known to curb appetites. Why is this so? Blue food doesn't exist in nature, with the exception of the blueberry. There are no blue vegetables, and hopefully, if you encountered a blue meat, you certainly wouldn't eat it. Because of this natural color deficiency, there is no automatic appetite response to anything blue.

There are colors that can put us in a better mood, too. Green is the most restful color for the eye. It has the power to soothe and comfort. Studies have even shown that people who work in surroundings that are green experience fewer headaches, stomach aches, and other signs of sickness or fatigue.

Out of Sight!
Besides being pretty to look at, colors and the light they come from really do have the power to impact people in many ways. Along with the aesthetics of light and color, there is real science behind each and every sight we see. Each flash or ray of light, each shade of color that light makes visible, and each time our eyes receive the messages to see them, we are reminded of a special relationship—one that is often overlooked because we simply take seeing for granted. We miraculously experience a bright, vivid world because of the workings of our eyes, the wonders of light, and the brilliance of color.

Now that you understand more about Light and Color,check out some colorful facts about Rainbows!

Here are some other sites about Light and Color that you may want to explore:

• Color and the Spectrum
• Make a Splash with Color
• Star Light, Star Bright Teacher Page: Science Background
• Bob Miller's Light Walk
• The Eyes Have It
• ColorTools.net