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# Science Fair Project 2012

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## Nejra Dedovic

on 3 December 2012

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#### Transcript of Science Fair Project 2012

photo credit Nasa / Goddard Space Flight Center / Reto Stöckli How fast does light travel through gelatin Speed of Gelatin Abstract For my science project, (how fast does light travel through gelatin), We had to use a combination of basic understanding of trigonometry and a basic understanding of Snell’s law of refraction. When we first began this project, we started off by of course using one night to make a hardened bowl of jell-O. Then the next day, I placed the jell-O in a medium sized Ziploc container. Then I took a low powered laser pen and shined it through the dark red jell-O. If you did this correctly like I did, you could vividly see the red beam shining through the jell-O. The purpose of this project, how fast does light travel through gelatin, is to find the velocity of light through gelatin by using Snell’s law of refraction. In order to do this, We have to use Snell’s equation, n1 (sin 01) =n2 (sin 02). Using this equation will help me find the index of refraction in gelatin. From there, we just divide the speed of light through a vacuum, which is 186,282, by 1.33, which is the index of refraction in red gelatin, which gets you 140,000 miles per second in red gelatin. So the velocity of light through red gelatin is 140,000. Our hypothesis is that we think that when you shine a laser pen through the gelatin, that the speed of it will decrease dramatically, but will seem to have had no effect to the naked eye, because the light is traveling at the speed of light, which is way beyond our ability to see. This will happen because of the chemical make up in the red gelatin. But in order to prove my theory right, we’ll have to use Snell’s equation, n1 (sin 01) =n2 (sin 02) to find the index of refraction in red gelatin. From there, we will use the index of refraction and divide it by the speed of light to find the speed of light in gelatin Review of Literature Light travels very rapidly, but it does have a finite velocity. In vacuum, the speed of light is 186,282 miles per second. However, when talking about the incredible distances in astronomy, the finite nature of light's velocity becomes readily apparent. It takes about two and a half seconds, for instance, for a radio communication travelling at the speed of light to get to the moon and back. Physics experiments over the past hundred years or so have demonstrated that light has a dual nature. In many instances, it is convenient to represent light as a "particle" phenomenon, thinking of light as discrete "packets" of energy that we call photons. Now in this way of thinking, not all photons are created equal, at least in terms of how much energy they contain. Each photon of X-ray light contains a lot of energy in comparison with, say, an optical or radio photon. It is this "energy content per photon" that is one of the distinguishing characteristics of the different ranges of light described above. Even though it is not strictly correct, it is hard not to think of a beam of light as a collection of little "light bullets" all strung together in a row. Materials 1. A device that produces a visible laser beam, such as a laser pointer or a laser level.
2. A mounting device on which the laser device rests that can easily indicate where the beam is pointed (it will be difficult to actually see the laser beam passing through air).
3. A protractor or a homemade protractor that can easily indicate the angle of refraction inside the gelatin.
4.Gelatin, a clear or a light/transparent color would generally work best
5. Plastic containers to mold the gelatin Procedure Results 1. First, come up with your own experimental setup. In addition to understanding the theory behind the experiment, this project calls for much experimental design creativity
2. Make my gelatin extra hard
3. Mount the laser pointer on a pre-made device that will indicate where the beam is going and what the angle of incidence is
4. Fix the laser device and record the angle of incidence with respect to the normal.
5. Shine the laser through the gelatin (you may need another person to help out by holding down the button if you use a simple laser pointer) and measure the angle of refraction inside the gelatin.
6. Find the speed of light in gelatin: first use Snell's law to calculate the index of refraction of the gelatin and then apply the definition of index of refraction to find the speed of light in the medium. Purpose & Hypothesis When we shined the laser through the red gelatin, you could see refraction taking place, there was an estimated 25 degree of refraction. Of course it differs with how much Jell-O in the container, and we’d say It had a medium amount of jell-O. So we used Snell’s law of refraction to find the index of refraction in red gelatin, which later was founded to b 1.33. With this, we just divided the velocity of light through a vacuum which is 186,282 miles per second by 1.33, which is the index of refraction in red gelatin, and we got 140,000 miles per second through red gelatin. In conclusion, during this project, we’ve had to learn a lot about trigonometry and eleventh grade physics. This had to be accomplished so that in the end, we could find the velocity of light through red gelatin. So we had to use Snell’s law of refraction and his/her equation, (n1 (sin 01)=n2(sin 02), to find the index of refraction in jell-O which was 1.44. Once we got the index of refraction in red jell-O, we just divided the velocity of light through a vacuum which is 300,000 kilometers per second by 1.44, which is the index of refraction in red gelatin, and we got 229,000 kilometers per second through red gelatin. This is in fact, what we stated in my hypothesis that light speed through red gelatin would in fact decrease dramatically, but is still no different to the human eye. InConclusion
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