ch28_esjp


 * // Chapter 28- Color //**

Sections:  **//Ch. 28 Section 1-The Color Spectrum//**
 * 1) The Color Spectrum
 * 2) Color by Reflection
 * 3) Color by Transmission
 * 4) Sunlight
 * 5) Mixing Colored Light
 * 6) Complementary Colors
 * 7) Mixing Colored Pigments
 * 8) Why the Sky is Blue
 * 9) Why Sunsets are Red
 * 10) Why Water is Greenish Blue
 * 11) The Atomic Color Code - Atomic Spectra


 * <span style="font-family: Georgia, serif;">__spectrum__- for sunlight and other white light, the spread of colors seen when the light is passed through a prism or diffraction grating. In general, the **spread of radiation by frequency**, so that each frequency appears at a different position.
 * <span style="font-family: Georgia, serif;">The spectrum of colors in white light (in order) are: red, orange, yellow, green, blue, and violet.
 * <span style="font-family: Georgia, serif;">They can be seen and separated by use of a prism (as seen below)
 * <span style="font-family: Georgia, serif;">__white light__- light, such as sunlight, that is a **combination of all the colors**. Under white light, white objects appear white and colored objects appear in their individual colors.
 * <span style="font-family: Georgia, serif;">This means that white is not a color itself, and instead it is a combination of all of the colors of light.
 * <span style="font-family: Georgia, serif;">In addition to white, this also means that black is not a color, but only an absence of light.

<span style="font-family: Georgia, serif;">**//Ch. 28 Section 2- Color by Reflection//**

<span style="font-family: Georgia, serif;">The colors of objects that we see everyday depends on the way that they reflect light that is shine upon them. Keep in mind that electrons can be forced into larger orbits by vibrations of electromagnetic waves, and therefore send out their own energy waves in all directions.
 * <span style="font-family: Georgia, serif;">All materials have their own natural frequencies for absorbing and emitting radiation.
 * <span style="font-family: Georgia, serif;">When the electrons reach a material where amplitudes of oscillation are large, the light is then absorbed.
 * <span style="font-family: Georgia, serif;">However, above and below the resonant frequency, the electrons (light) is reemitted.
 * <span style="font-family: Georgia, serif;">In transparent objects, the reemitted light passes through
 * <span style="font-family: Georgia, serif;">In solid (or opaque) objects, the light goes back to the medium where it came from (reflection)
 * <span style="font-family: Georgia, serif;">White objects reflect all colors, while black absorbs all colors.
 * <span style="font-family: Georgia, serif;">For objects that reflect a cerain color, in this case, some most colors are absorbed, and one color is reflected (the one you see)
 * <span style="font-family: Georgia, serif;">However, most objects do not reflect only one frequency, but instead several.
 * <span style="font-family: Georgia, serif;">Yellow can be made by absorbing blue and violet, and reflecting red, green, and yellow.
 * <span style="font-family: Georgia, serif;">It is crucial to remember that colors can be changed by the illuminating light being used.
 * <span style="font-family: Georgia, serif;">In candle light, something may appear more yellow, while under fluorescent light, it may appear more blueish.


 * //<span style="font-family: Georgia, serif;">Ch. 28 Section 3- Color by Transmission //**

<span style="font-family: Georgia, serif;">**//Ch. 28 Section 4- Sunlight//**
 * <span style="font-family: Georgia, serif;">__pigment__- a material that selectively **absorbs colored light**.
 * <span style="font-family: Georgia, serif;">An object with a certain color pigment will absorb all other colors except it's own pigment, which it then transmits.
 * <span style="font-family: Georgia, serif;">For example, in glass of certain colors, only the color of the glass is transmitted, and all other colors are absorbed, therefore only letting through some of the light.
 * <span style="font-family: Georgia, serif;">This happens because the light from the other frequencies are reemitted from atom to atom.

<span style="font-family: Georgia, serif;">-The sun gives off white light, which is a combination of all colors of light. -Although we might believe at first that the brightnesses of each color are even, we are mistaken.
 * <span style="font-family: Georgia, serif;">-In actuality, the lowest frequencies of light (red and orange) are not nearly as bright as yellow and green.
 * <span style="font-family: Georgia, serif;">-Because of this, yellow-green is actually the brightest part of sunlight (of which we are most sensitive to)
 * <span style="font-family: Georgia, serif;">-In addition to reds and oranges, the opposite end made up of blue and violet is also not as bright.
 * <span style="font-family: Georgia, serif;">-All of this is easily seen through a distribution of brightness verses frequencies in a **radiation curve** of sunlight.
 * <span style="font-family: Georgia, serif;">-This can be seen on page 426 of the text book.

Ch. 28 Section 5- Mixing Colored Light //**
 * //<span style="font-family: Georgia, serif;">


 * <span style="font-family: Georgia, serif;">__additive primary colors__- red, blue and green light. These colors when added together produce white light.
 * <span style="font-family: Georgia, serif;">This means that any color can be made with these three colors by adjusting the brightness of each one on the screen.
 * <span style="font-family: Georgia, serif;">Televisions are made this way in order to produce any color on the screen. By combining red, blue, and green very small lights and differing brightness, an image can be produced.

<span style="font-family: Georgia, serif;">**//Ch. 28 Section 6- Complementary Colors//**

<span style="font-family: Georgia, serif;">
 * <span style="font-family: Georgia, serif;">When three additive primary colors of light are mixed, they produce white.
 * <span style="font-family: Georgia, serif;">However, when only two out of the three are mixed, they produce complementary colors.
 * <span style="font-family: Georgia, serif;">red + green = yellow
 * <span style="font-family: Georgia, serif;">red + blue = magenta
 * <span style="font-family: Georgia, serif;">blue + green = cyan
 * <span style="font-family: Georgia, serif;">When two of these new colors add together to make white, then they are described as complementary colors.
 * <span style="font-family: Georgia, serif;">This means that every color also has a complementary color that produces white.
 * <span style="font-family: Georgia, serif;">Also, if you subtract a color from white light, this results in that color's complementary.
 * <span style="font-family: Georgia, serif;">yellow + blue = white
 * <span style="font-family: Georgia, serif;">magenta + green = white
 * <span style="font-family: Georgia, serif;">cyan + red = white

Ch. 28 Section 7- Mixing Colored Pigments //**
 * //<span style="font-family: Georgia, serif;">

<span style="font-family: Georgia, serif;">
 * <span style="font-family: Georgia, serif;">__subtractive primary colors__- the colors of magenta, yellow and cyan. These are the three colors mose useful in color mixing by subtraction.
 * <span style="font-family: Georgia, serif;">Although a combination of these colors produce white in light, in pigments, they instead create different colors.
 * <span style="font-family: Georgia, serif;">This is because they instead absorb a lot of colors and only reflect their respective "pigment" color or mixtures of colors.
 * <span style="font-family: Georgia, serif;">As an example: Blue paint reflects blue light, but also violet and green. It also absorbs blue and violet light. However, when it is mixed with yellow paint, it reflects green light and absorbs all other colors.
 * <span style="font-family: Georgia, serif;">This concludes that mixing color with light is **additive**, and mixing with colors is **subtractive.**


 * //Ch. 28 Section 8- Why the Sky is Blue//**

<span style="font-family: Georgia, serif;">-First of all, it is important to remember that atoms and molecules reemit light waves that shine on them, and particles do the same. -Because the particles are so tiny, the nitrogen and oxygen molecules as well as particles reemit light and is scattered when sun is shined upon them.
 * <span style="font-family: Georgia, serif;">__scatter__- to absorb sound or light and **reemit it in all directions **
 * <span style="font-family: Georgia, serif;">The little ultraviolet light that passes through the upper atmosphere and to the lower is then scattered by the particles in the air.
 * <span style="font-family: Georgia, serif;">The high frequency colors (violet, blue) are scattered most, and lower frequencies are scattered the least.
 * <span style="font-family: Georgia, serif;">However, the color of the sky also depends on the amount of dust particles which scatters lower frequencies more.
 * <span style="font-family: Georgia, serif;">Also, the higher in the sky, the less molecules, and therefore darker sky
 * <span style="font-family: Georgia, serif;">When there are no molecules (space) the sky is black
 * <span style="font-family: Georgia, serif;">Clouds are made of microscopic water droplets (all different sizes) and therefore result in different frequencies of scattered light.
 * <span style="font-family: Georgia, serif;">Low frequencies = large droplets
 * <span style="font-family: Georgia, serif;">High frequencies = small droplets
 * <span style="font-family: Georgia, serif;">They are bright because the small droplets vibrate together, which scatters more energy then if they had vibrated separately.


 * //<span style="font-family: Georgia, serif;">Ch. 28 Section 9- Why Sunsets are Red //**

<span style="font-family: Georgia, serif;">Air is made up of nitrogen and oxygen molecules; these molecules most easily transmit lower frequencies of light.

Therefore, reds, oranges, and yellows pass through thick atmospheres (which occur during sunset and sunrise) while the others are scattered.


 * <span style="font-family: Georgia, serif;">When the sun is most horizontal to the horizon, the light that must reach the earth must pass through the most amount of atmosphere, only allowing reds through the air. This is also why sunsets are always these colors!

<span style="font-family: Georgia, serif;">

//**Ch. 28 Section 10- Why Water is Greenish Blue**//

<span style="font-family: Georgia, serif;">Water is clear to all of the visible frequencies of light, not blue. This is because water molecules abosorb infrared light waves that resonate to the frequencies of the infrared waves. This energy from the infrared waves are then formed into kinetic eneregy of the water molecules, and then causes a gradual absorption of red light. >
 * <span style="font-family: Georgia, serif;">This process leaves the complementary color of red, cyan, which happens to be a greenish blue color.
 * <span style="font-family: Georgia, serif;">This shows how any color of anything is depended on what colors are reflected by molecules, and also which are absorbed. [[image:http://www.wallpaperstwist.com/albums/userpics/10001/normal_Ocean_Wave.jpg align="center" caption="Greenish blue ocean"]]


 * //<span style="font-family: Georgia, serif;">Ch. 28 Section 11- The Atomic Color Code - Atomic Spectra //**

<span style="font-family: Georgia, serif;">All elements have their own unique color when they emit light. They are most easily seen and analyized when in their gaseous state. This is because the atoms are far enough apart to emit their true colors. <span style="font-family: Georgia, serif;"> <span style="font-family: Georgia, serif;">
 * <span style="font-family: Georgia, serif;">__spectroscope__- an instrument used to **separate the light from a hot gas** or other light source into its constituent frequencies.
 * <span style="font-family: Georgia, serif;">By using a thin slit, several lenses, and a prism, one can separate the gaseous light into separate frequencies.
 * <span style="font-family: Georgia, serif;">They appear as a series of lines indicating the basis of the entire color of the element.
 * <span style="font-family: Georgia, serif;">__line spectrum__- pattern of **distinct lines of color, corresponding to particular wavelengths**, that are seen in a spectroscope when a hot gas is viewed.
 * //Sources//**


 * [|www.scittscience.co.uk]
 * <span style="font-family: Georgia,serif;">Conceptual Physics: Third Edition with Expanded Technology by Paul G. Hewitt
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 * optics.kulgun.net
 * [|www.indiamart.com]
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