Purpose

Hypothesis

Experimental design

Materials

Backround Report

Results

Analysis and Conclusion

Bibliography

My hypothesis is that the florescent grow light will cause the zinc sulfide to re-emit more luminescence. Compared to all the other light sources. I also think the incandescent light will illuminate the zinc sulfide less than all the other light sources.

The manipulated variable is the different light bulbs The responding variable is the light re-emitted by the zinc sulfide plate Control group contains the incandescent light bulb. I am measuring the strength of luminescence given off by the Zinc Sulfide measured by the light meter and Lab Pro The constants of this experiment are: the frequency of light, the time of testing, the time the zinc sulfide was charged, the same area (the middle) being tested, and the same computer program and light meter. The limitations to this experiment are the light sources and the phosphors available to test. 

The results indicate that the incandescent and yellow light bulb put out a large amount of infrared light because IR-light reduces the luminescence given off of the zinc sulfide. The mineral light bulb gave off more ultraviolet light because when the mineral bulb was used to charge the zinc sulfide the luminescence was enhanced compared to the incandescent light bulb. 

2. Turn off all room light and turn on the test light.

3. Have the yardstick ready and know what the distance is for the specific light source. (The distance of the light should be known by experimenting before hand, each light should have a frequency of 100 lumens with a error of 10 on each side) 

4. Expose the zinc sulfide to the light source and start the stopwatch for 30 seconds. 

5. When the 30 seconds are up immediately turn off the test light and put the light meter on the designated area. (The middle)

6. Press the collect button on the computer at the same time as step five. In order to do all this, it is handy to have a helper. 

7. Hold the light meter steady while the data is being collected-the collection will take 30 seconds that should be already programmed into the computer. 

8. After the data is collected, be sure to put the zinc sulfide back in the dark place before turning on the main light room so it doesnÕt charge more. Let the zinc sulfide stay in the dark for 3-5 minutes or until the zinc sulfide is not glowing.

9. To find the median of the luminescence of the zinc sulfide for the 30 second time period go to linear fit by going from the analyze and down to linear fit. Make sure the zinc sulfide is not glowing any more. And prepare for the next test 

10.Do steps 1-9 for each light bulb three times. 

11.Find the average of the three tests of each light source. 

There are many different things that light does. Light can be absorbed reflected refracted and can pass through an object. Light is what lets us see color and the world around us. The light spectrum is part of this. Because of the light spectrum and itÕs different waves phosphorescence happens. This is when a phosphor is charged and re-emits the waves at a different length causing it to glow. Light spectrum, light absorption and phosphorescence tie together in a way one my never would have expected. 

The light spectrum includes long, short, and visible waves. The energy of a light relates to how strong the frequency is. In the light spectrum the human eye cannot perceive the light waves because of their frequencies. There is only one part of the spectrum that is visible and its size is very small. Before the visible spectrum the frequency is less and it is called infrared light and on down the spectrum comes radio waves. The energy of the infrared light is almost all turned into heat energy. The infrared light from the sun is what warms the earth up. The visible spectrum has a certain order of light waves, it goes from highest to lowest frequencies red, orange, yellow, green, blue, and violet. These visible light waves are what we see as color. After the highest frequency (violet) in the visible spectrum ultraviolet light comes next that is not in the visible part of the light spectrum. Ultra violet light and infrared light waves and other type of waves are invisible to the human eye because the UV-light has such a high frequency and the IR-light is so low a frequency it is the same with the other types of waves also. Ultraviolet light comes from the sun and man-made light bulbs like fluorescent and mercury lights. The suns light is white but when the light is put through a prism the light is separated into the visible spectrum. When all the colors of light from the visible spectrum are put together through another prism the light becomes white or colorless again. White light has no certain frequency it is made up of the color frequencies. Isaac Newton made this discovery. This means that the sun has all the colors in it so when it reflects off of objects; the objects true color is shone. In some lights like fluorescent and incandescent lights there may not be all the colors in them so objects may appear to be different colors than they really are. Light has both electric and magnetic fields so the light is also referred as the electromagnetic field. From howstuffworks.com

All objects absorb light to some degree. The material is not all that matters in its absorption of light. It is how the light affects the molecules and atoms of that specific material. The absorption is turned into internal energy inside the material. This internal energy is then turned into often times heat, thermal energy, and in some cases chemical energy like in photochemistry. When this process takes place the energy is re-emitted in the same wavelengths. When the same wavelengths are re-emitted this is identified, as scattered light. Two of the exceptions to this are fluorescence and phosphorescence; these materials re-emit the Òindecent radiationÓ energy (the light that hits the material) at longer wavelengths. What you see when the material absorbs the light depends on the length of the waves and how the light hits the object. Even though a material is transparent it also absorbs light to some extent. An example of this would be when light travels through water. How much light a material absorbs is dependant on the length of light waves and how the light hits the surface of the material. This means an object could absorb more ultraviolet light versus infrared light. How much or what type of light be it invisible or visible depends on the material or substance absorbing the light. There is an absorption spectrum and spectroscopist use this to find the structure of the absorbing material. The light absorption of a material can be measured by a colorimeter. Another measuring tool to measure absorbed light is called a spectrophotometer The colorimeter is used usually for only visible light waves while the spectrophotometer can also comprehend further wavelengths such a s infrared radiation and ultraviolet light. The absorption spectrum is often used in identifying chemical compounds. 

The definition of phosphorescence from The Visual Dictionary of Physics (1995) defines phosphorescence as Òa type of luminescence in which a substance glows with visible light some time after being exitedÓ. There are 3 main characteristics of phosphors 1. The phosphors are required to be charged or energized by a certain type of energy. 2. They produce a certain color of visible light; some examples are green, orange, red, yellow, and or a mixture of the colors. The form of energy that it is charged with can cause color difference, and what the substance is made of. 3. The persistence of the phosphor, that is how long the phosphor glows after being energized. Two examples of phosphors are strontium aluminate and zinc sulfide. These chemicals along with others are used in glow in the dark toys and other things. The electrons in the phosphor become excited or energized by the light waves either short or long. The wavelengths are lengthened and the electrons go back to the lower energy orbital over a long period of time. When this occurs phosphorescence happens, and luminescence is given off. This is phosphorescence, when the light of specific substances is given off when they absorb energy. Many different things including electricity, light, ultraviolet radiations and an X-ray beam energize the electrons. Fluorescent and phosphorescent may get confused often but there are many differences. One of the differences is the length of time it takes for the glow to disappear. Florescence is when a substance glows with visible light immediately after being excited by invisible ultra violet radiation. In the fluorescent light bulbs the electricity charges the atoms instead of using heat like on incandescent lights. Phosphorescence is not only found in toys but also TVs, and computer screens. These phosphors are charged by electricity just like the fluorescent lights. Minerals that are phosphorescent are barium sulfide, calcium sulfide and strontium sulfide. 

There are a few different ways to measure light. Lumens is a measurement that measures the flow of light from the source of light. Lumens have to do with how lighting efficiency is indicated according to its relation to the power consumed. Another way to measure it is in Hertz. A candela is the luminous intensity in any direction. The measurement of lumens has to do with frequency. Frequency is the amount of waves passing a point in space during any time. Miscellaneous Light waves are waves of energy. These waves of energy are what travel, bounce off, and are absorbed into or onto things. Electric current passing through a gas such as incandescent, fluorescent, metal halide, high-pressure sodium and mercury vapor most commonly emits light. Energy and light are very closely related. 

Light is what helps us live and enjoy the world around us. Absorption of light is what causes phosphorescence. And phosphorescence is caused when energy excites the atoms and as the atoms slow down a glowing luminescence is given off. Light has many jobs and does many things that we have still to discover we should start learning about it so that some day we can light the world with our knowledge of light and discover its mysteries. 

The data shows that the mineral light charged the zinc sulfide significantly more than the others.  The incandescent light and the yellow light least charged the zinc sulfide. The black, green, and red lights illuminated the zinc sulfide identically.  The florescent grow light when it charged the zinc sulfide the luminance given off was very close to the black green, and red lights.
 
 

Becker, Ralph S. "Phosphorescence." World Book. Chicago: Child Craft International, 1978. 363-364. 

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how stuff works . 29 Nov. 02 <http://www.howstuffworks.com/question388.htm>. 

"Phosphorescence, luminescence, florescence." The Visual Dictionary of Physics. London: Dorling Kindersley Limited, 1995. N. pag. 
Simon, Hilda. The Magic of Color. New York: Jacket Illustration, 1981. 
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