What Suntan Lotion is and How it Works By: Ceren I. 2012
What is Suntan Lotion?
Suntan lotion is a lotion that absorbs or reflects the sunlight that comes in contact with the skin preventing sunburn. Suntan lotion has organic chemical compounds in it which is what absorbs ultraviolet light from the sun. It also has inorganic particulates in it that also absorb UV light but also reflect or scatter it. Some of the inorganic particles may be titanium dioxide, zinc oxide, or a combination of both. Organic particulates mostly absorb light like the organic chemical compounds do, but organic particulates contain multiple chromophores, may reflect and scatter some of the light like inorganic particles do.

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Figure 1: The Difference between Sun Block and Sun Tan Lotion
Why do we need Suntan Lotion?
We need suntan lotion, or sunscreen, to protect us from the worst of the sun’s radiation. Ultraviolet light is that radiation that comes from the sun. Suntan lotion, or sunscreen, doesn’t allow all of that radiation to get to our skin.

How it Works
UV-A radiation produces a slow tan. UV-B radiation works faster than UV-A radiation and it affects the outer layer of skin. Different suntan lotions or sunscreens have different effects, some allow a little bit of tanning some are meant to completely block out UV light. Suntan lotion or sunscreen has P-aminobenzoic acid (PABA or ABA) in it. PABA absorbs UV-B radiation while letting UV-A through resulting in just a slow tan. Benzophenone, oxybenzone, and dioxybenzone are other compounds that absorb UV light.
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Figure 2: The Light Spectrum Scale and a Diagram of How Sunscreen Works

Ultraviolet Light
Ultraviolet light is an electromagnetic wave produced by the sun. Ultraviolet waves have shorter wave
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Figure 3: The Difference between UVB Sunscreen and Broad-Spectrum Sunscreen
lengths and higher frequencies than visible light does. The greater the frequency of the UV waves, the higher its energy. The wavelengths of the ultraviolet waves vary between 60 nm and 400 nm. Ultraviolet light affects your body in both good and bad ways. Bad effects can be that too much ultraviolet light can cause sunburn. Too much ultraviolet light can also cause skin cancer, wrinkles, and damage to the eyes. (Note: In the image above Ultraviolet light would be found in the purple section.)
Most of the sun’s ultraviolet light does not reach the Earth’s surface, though. You should still protect yourself from the ultraviolet light that does reach the Earth with sunglasses and with sunscreen that has a high SPF (sun protection factor) for that purpose. UV light can travel through clouds, so don’t expect clouds to protect you. UV light does have good effect too though. UV waves produced by ultraviolet lamps are used to kill bacteria on food and tools that were used during surgery. Small amounts of UV light make your skin cells produce vitamin D, which is good for your teeth and bones.


Glossary:
Amorphous: Without shape: without any clear shape, form, or structure.
Benzophenone: A crystalline, water-insoluble ketone.
Chemical Compounds: A substance formed by chemical union of two or more elements or ingredients in definite.
Chromophores: Any chemical group that produces color in a compound.
Compound: A mixture: something made by combining two or more things
or a chemical substance: a substance formed by the chemical combination of elements in fixed proportions.
Crystalline: Resembling or being crystals: relating to, made of, containing, or resembling crystals very clear.
Dioxybenzone: A sunscreen that absorbs throughout the ultraviolet spectrum.
Electromagnetic: Anything of or pertaining to electromagnetism or electromagnetic fields.
Folic Acid: Vitamin B.
Frequencies: The number of cycles or completed alternations per unit time of a wave or oscillation.
Inorganic: Of or relating to compounds not containing hydrocarbon groups.
Insoluble: Not dissolvable: not dissolvable: incapable of being dissolved in a liquid.
Ketone: An organic compound.
Oxybenzone: A sunscreen that absorbs UVB radiation and some UVA radiation.
Organic Chemical Compound: Any member of a large class of chemical compounds whose molecules contain carbon.
Organic: Of, relating to, or denoting compounds containing carbon.
P-aminobenzoic Acid: A substance required for the synthesis of folic acid by many organisms.
Particulates: Matter in such a form.
Synthesis: The result of combination.
Titanium dioxide: A white, water-insoluble powder used in white pigments, plastics, and ceramics.
Ultraviolet Light: Radiation lying in ultraviolet range: wave lengths shorter than light but longer then x-rays.
Zinc oxide: A white or yellowish-white, amorphous, odorless, water-insoluble powder.



Citations:
Website: "Sunscreen." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 27 Sep. 2012. Web. 27 Sep. 2012.
Books: Snyder, Carl H. The Extraordinary Chemistry of Ordinary Things. New York: John Wiley, 1998. Print
Dumas, Leila. Sound and Light. Orlando: Holt, Rinehart and Winston, 2007. Print
Database: "radiation." Compton's by Britannica. Encyclopædia Britannica Online School Edition.
Encyclopædia Britannica, Inc., 2012. Web. 27 Sept. 2012.
Image: http://www.open.edu/openlearn/files/ole/imported/o_46959/sunblock4.gif
Image: http://www.skinlaboratory.com/media/video/u_sunscreen_04.jpg