ch28_ow

** Chapter 28 - C o l o r   **

 * 28.1 - The Color Spectrum **

If you shine a beam of white light through a triangular prism, you can see the light bend and split up by color into a spectrum. Red light bends least, violet light bends most, and in between the order will be red, orange, yellow, green, blue, and violet.

If all the colors of the spectrum were combined, the result would be white light. If all light is removed, the result is black.
 * 28.2 - Color by Reflection**

When light shines on an object, some will be absorbed, and some will be reflected. Depending on the material the object is made of, some wavelengths will be absorbed more than others, and the remaining ones will be reflected. The colors of light that are reflected will be the ones that you see when you look at the object.

If you shine red light on an object, you will only see red reflected back. No other colors are possible besides the ones shining on the object.


 * 28.3 - Color by Transmission **

If white light shines through a transparent object, some wavelengths will be absorbed while others will pass through. The energy carried colors absorbed by the object will be turned into heat and will cause its temperature to slightly increase.


 * 28.4 - Sunlight **

Light from the sun is a composite of all of the visible frequencies as well as many others that we cannot see. The brightest colors coming from the sun are yellow and green with slightly less intensity as the freqencies move away from that point. Because humans developed in that light, we are most sensitive to those frequencies. This increased sensitivity is why many emergency vehicles such as fire engines are being painted that color.
 * 28.5 - Mixing Colored Light **

The primary colors of light are red, blue, and green. All three together produce white light, red and green produce yellow, red and blue produce magenta, and blue and green produce cyan.


 * 28.6 - Complimentary Colors**

Complimentary colors are pairs of colors that together include each primary color once. For example, cyan is complimentary to red. When two complimentary colors of light are mixed the result is white light.


 * 28.7 - Mixing Colored Pigments**

Pigments work by absorbing the complimentary colors to the ones that they reflect. A cyan pigment will absorb red light and reflect blue and green.

If two pigments are mixed, the resulting pigment will absorb all colors absorbed by either of the pigments, this is known as mixing by subtraction. If yellow pigment is mixed wth cyan the resulting pigment will absorb both blue and red and will reflect green light.

The subtractive primary colors are cyan, magenta, and yellow.


 * 28.8 - Why The Sky Is Blue **

As light passes through microscopic particles in the upper atmosphere some of the light will be absorbed and reemitted (scattered) by the particles it passes through. The shortest wavelengths of light (violet and blue) are scattered the most, causing the sky to appear blue. The remaining colors of light (the longer wavelengths from green to red) will shine through causing the sun to appear yellow.
 * 28.9 - Why Sunsets Are Red**

When the sun is low in the sky, the sunlight has a much longer path through the atmosphere to reach your eyes. This means that more of the light (longer wavelengths) will be scattered leaving only red and orange light to reach the earth's surface.




 * 28.10 - Why Water Is Greenish Blue **

Water absorbs a very small amount of red light. When you see a small amount of water (a bottle or glass of water), you are unlikely to notice the coloration but when you see a large amount of water together the absence of red makes the water look greenish blue or cyan.
 * 28.11 - The Atomic Color Code - Atomic Spectra**

Every element emits its own characteristic set of colors of light when it is heated in a gaseous state. If the light coming from some element is viewed through a spectroscope, then a pattern known as a line spectrum will be seen that is different for every element.