The Visible Light Spectrum Essay, Research Paper

“Mr. Petersuh-uh-uhn…. I need a white crayon for the white parts of the map!”, my daughter’s classmate whines as she peers into her box of mismatched Crayons. “Don’t worry about coloring those parts of the map. White isn’t a color anyways…”, replies her sixth grade teacher. Uh-oh. Big mistake! The entire class is now in for an impromptu lesson in the properties of light and the visible spectrum, courtesy of the child of a laser student. Added bonus: elevated egg-headed status for aforementioned child.

“Excuse me, Mr. Petersen, but I feel that I must correct you on that. You are sadly misinformed. My Mom says that white is the presence of all color and black is no color! What of that?! Hmmm?” (Yes…my kid really talks like this. She’s 10 and she skipped a grade level. She’s quite loquacious. I wonder where she gets it from? But I digress…)

The flustered Mr. Petersen flashes my child a weak smile and mumbles something to the effect of, ”…technically, Jacki, you are correct. Just leave the white parts blank and stay on task!” Shame, shame, shame. The instructor has just dropped the ball on a wide-open opportunity for learning and discussion.

Never one to miss an opportunity to exercise her mind and initiate a discussion/impress her peers, my kid goes on to explain the basic principles and properties of light and color. This precipitates a wave of “no way!” and “how’d you know?”s from the inherently curious and doubly impressed group of sixth graders.

As she, in fits and giggles (true sixth grade girl fashion!), recounted the story to me, she re-iterated over and over that “most grown ups just don’t know ANYTHING!”. And I thought to myself, “You know…we might know a lot about some things, but she just pointed out one of the most popular misconceptions that abounds concerning light and the perception of color!”. White light is NOT the absence of all color! Black is NOT all of the colors all mixed together! (Remember second grade? When you ran out of black crayon and just scribbled all of the remaining colors together and got a muddy brownish gray at best? Uh-uh…never works.)

Thus, I have taken it upon myself to enlighten the rest of us “just don’t know ANYTHING” grown-ups on the subject of color and the visible spectrum of light. Pay attention, class! This is Visible Light 101.

All light consists of waves traveling in space. The length of the waves determines the color of the light. Each color of light has its’ own characteristic wavelength and what is visible to the human eye is termed the visible spectrum of light. It begins on one end with the color red and goes through the spectrum to the color violet. The entire spectrum consists of the following colors: red, orange, yellow, green, blue, indigo, and violet. White light consists of a mixture of many different wavelengths. Try this: use a prism to disperse white light from a source such as a light bulb or flashlight into its’ separate component (colors).

The fact that we “see” a certain color at all is dependent on a couple of basic principles. First, ordinary colored light consists of a broad range of wavelengths covering a particular portion of the spectrum. When you isolate those wavelengths, by using a filter or a device that blocks the undesired wavelengths, you will see only the ones that are emitted when you view the light. A good example of this is a stop light… the green light emits the entire green portion of the spectrum plus a little of the neighboring yellow and blue regions.

Other reasons for seeing only certain colors are attributed to the four properties of light know by the acronym RATS. R.A.T.S stands for reflection, absorption, transmission, and scattering. Each of these processes occurs to some degree when light is incident upon a surface. In the case of the color white, most or all of the wavelengths are reflected back to your retina, allowing you to see the entire visible light spectrum. In the case of the color black, most or all of the available light that is incident upon the surface being viewed is absorbed by the surface. This leaves little or no part of the visible spectrum to be reflected back to your eye. So you see none, or very little of the visible spectrum. Impress your kid. Class dismissed.