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Red, White, and Blue

Red, White, and Blue: We are surrounded by these three colors during this first week of July.

And color is always a great topic for a science column, so let’s look into some of the science behind these festive holiday colors.

First, what is color?

The human eye is a wonderful thing, and it allows us to perceive a variety of what we call color. And, for humans, the visible spectrum is only a very small part of the overall electromagnetic spectrum.

Our eyes are adapted to pick up photons with energies that fall within a narrow band of wavelengths, 390 to 700 nanometers (nm). But, while the particular wavelength of light is perceived as a specific color, reds are in the 620 to 750 nm range, while blue is in the 450-495 nm, how we really see color and how we make a specific color on a computer screen or paper or in cupcake icing is a completely different matter.

To understand this a bit better, we have to understand how light interacts with objects and ultimately interacts with our eyes.

Light as from a computer screen or lightbulb may be emitted, i.e., energy in the form of light is radiated from the source. The ambient light, like light from the sun or our lightbulb, is bouncing around hitting various objects. When the ray of light hits an object, some of the light is absorbed, and some is reflected.

Let’s look at this a bit further, white light, like that from the sun, is comprised of the entire visible spectrum. If you pass this light through a prism or a raindrop, the light spreads out into the individual colors, and we perceive a rainbow. If the white light hits a stop sign, all of the colors that are not red, get absorbed by the sign, and the red light is reflected to our eyes, and thus we perceive the sign as being red. A black object absorbs all other colors, while a white object reflects all the colors.

Our eyes are our color detectors. The reflected light enters the eye and hits the retina which is covered in light-sensitive cells, rods, and cones.

The rods are responsible for vision in low light levels and are not sensitive to color. The cones are the receptors that sensitive to the particular wavelengths and give us our perception of color. They are also responsible for our high spatial acuity. And, our perception of colors is due to the sensitivity of these cells to particular wavelengths.

There are three types of cones — “red” sensitive, “green” sensitive, and “blue” sensitive. Most of the cones are “red” sensitive, about 64 percent, followed by the “green” sensitive ones, which make up about 32 percent and the remaining 2 percent are “blue” sensitive. The sensitive of each type is not limited to just one wavelength but a narrower distribution of wavelengths centered about a particular wavelength. The “red” sensitive cells are centered about 575 nm, which is more yellow than red. The “green” cells are centered about 535 nm and the “blue” cells about 445 nm.

Notice something about the colors, red, green and blue?

These are what we refer to as the “primary” colors or the RGB values that you see listed on your color picker when you are using a computer paint program.

You can mix these three primary colors because their additive properties allow us to produce any particular color that we want to see. It is these three color types that provide for the basis of color television, and color monitors. So, getting the right color on a screen is a function of selecting just the right mix of the red, green and blue.

Similarly, when dealing with paints, pigments, coatings and food colors, it is about getting the right mix of materials to allow for the reflection of the wavelengths of light to allow us to see a particular hue.

Then, there are the lighting and surrounding tricks to have our brains fill in a particular color. Remember the gold and white versus blue and black dress controversy? It is all about how our eyes capture the light and the signals that the receptors send to the brain, and ultimately how our brains analyze the data. But, today is a day for enjoying the photons, whether it is just being outside, or enjoying the decorations, or the fireworks.

Editor’s note: This is a series of science-related articles by author Frankie Wood-Black, Ph.D., REM, MBA, to appear in Mid-Week section of the Ponca City News. The author currently runs her own environmental consulting firm based in Ponca City, Sophic Pursuits, Inc., and also serves as a Physics Instructor and the Director for Process Technology at Northern Oklahoma College.

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