Light+and+Color

 ​ ** Light and Color **

How does light travel? What is the Electromagnetic Spectrum? What’s the difference between light color and pigmentation? First Things First... __** To understand light and color, you must know something about waves. Check this out. [|Waves]
 * __ Essential Questions: __**
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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.



**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. The colors of light happen to be the only wavelengths that our eyes can see, but there are other wavelengths that we cannot see.

Light waves also come in many frequencies. The ** frequency ** is the number of waves that pass a point in space during any time interval, usually one second. It is measured in units of cycles (waves) per second, or Hertz (Hz). The frequency of ** visible light ** is referred to as ** color **, and ranges from 430 trillion Hz, seen as red, to 750 trillion Hz, seen as violet. Again, the full range of frequencies extends beyond the visible spectrum, from less than one billion Hz, as in radio waves, to greater than 3 billion billion Hz, as in gamma rays. Light waves are waves of energy. The amount of energy in a light wave is proportionally related to its frequency: High frequency light has high energy; low frequency light has low energy. Thus gamma rays have the most energy, and radio waves have the least. Of visible light, ** violet ** has the most energy and ** red ** the least. Light not only vibrates at different frequencies, it also travels at different speeds. Light waves move through a vacuum at their maximum speed, 300,000 kilometers per second or ** 186,000 miles per second **, which makes light the fastest phenomenon in the universe. Light waves slow down when they travel inside substances, such as air, water, glass or a [|diamond]. The way different substances affect the speed at which light travels is key to understanding the bending of light, or refraction, which we will discuss later. So light waves come in a continuous variety of sizes, frequencies and energies. We refer to this continuum as the ** electromagnetic spectrum **.



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.
 * __Light Transfer__** 

**__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 **<span style="font-family: Jester; font-size: 13pt; mso-ansi-language: EN-US; mso-bidi-font-family: Arial; mso-bidi-language: AR-SA; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-US;"> (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.

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.
 * __ Pigment 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. To see it another way, view these video clips.
 * __ Light Color __**

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<span style="font-family: Jester; font-size: 13pt; mso-ansi-language: EN-US; mso-bidi-font-family: 'Times New Roman'; mso-bidi-font-size: 12.0pt; mso-bidi-language: AR-SA; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-US;"> As stated previously, the primary colors of light are red, blue, and green. These occur in the **<span style="font-family: Jester; font-size: 13pt; mso-ansi-language: EN-US; mso-bidi-font-family: 'Times New Roman'; mso-bidi-font-size: 12.0pt; mso-bidi-language: AR-SA; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-US;">Additive Color (RGB) Model **<span style="font-family: Jester; font-size: 13pt; mso-ansi-language: EN-US; mso-bidi-font-family: 'Times New Roman'; mso-bidi-language: AR-SA; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-US;">, 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.
 * __Additive Color__** <span style="font-family: Jester; font-size: 13pt; mso-ansi-language: EN-US; mso-bidi-font-family: 'Times New Roman'; mso-bidi-language: AR-SA; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-US;">

<span style="font-family: Jester; font-size: 13pt; mso-ansi-language: EN-US; mso-bidi-font-family: 'Times New Roman'; mso-bidi-font-size: 12.0pt; mso-bidi-language: AR-SA; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-US;">**__Subtractive Color__**
 * The Subtractive Color (CMYK or CMY) Model**<span style="font-family: Jester; font-size: 13pt; mso-ansi-language: EN-US; mso-bidi-font-family: 'Times New Roman'; mso-bidi-language: AR-SA; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-US;"> 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 //<span style="font-family: Jester; font-size: 13pt; mso-ansi-language: EN-US; mso-bidi-font-family: 'Times New Roman'; mso-bidi-font-size: 12.0pt; mso-bidi-language: AR-SA; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-US;">doesn't //<span style="font-family: Jester; font-size: 13pt; mso-ansi-language: EN-US; mso-bidi-font-family: 'Times New Roman'; mso-bidi-language: AR-SA; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-US;"> absorb.

__**"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 **<span style="font-family: Jester; font-size: 13pt; mso-ansi-language: EN-US; mso-bidi-font-family: 'Times New Roman'; mso-bidi-font-size: 12.0pt; mso-bidi-language: AR-SA; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-US;">shadow **<span style="font-family: Jester; font-size: 13pt; mso-ansi-language: EN-US; mso-bidi-font-family: 'Times New Roman'; mso-bidi-language: AR-SA; mso-fareast-font-family: 'Times New Roman'; mso-fareast-language: EN-US;">. 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.

Some people have trouble discerning colors, along with their shades and luminance. ** Color blindness ** is a color perception problem whose most common ailment is a red-green deficiency. This means that there is a lack of red or green photopigments and people have difficulty making out colors that are based on the `red to green' ratio. It is estimated that about 7% of all males are color blind, while only .4% of women are affected. This is because the defect is linked to the X-chromosome, of which males only have one, so there is less chance of it being naturally corrected by the genes.
 * __ Color Trouble __**

Take an informal color blind test!

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