## Measuring and incidence. Snell’s law says that the

Measuring the Speed of Light in different mediums Physics Experimental Investigation ___________________________________________Signature of Sponsoring Teacher ___________________________________________Signature of School Science Fair Coordinator TeacherRonil Chaudhary640 W. Scott St.Chicago, IL 60610Grade #8 Table of ContentsAcknowledgments                                                                                         Page 3Purpose and Hypothesis                                                                                Page 4Background Research                                                                                    Page 5Materials and Procedure                                                                                Page 6Results                                                                                                          Page 7Conclusion and Reflection                                                                             Page 8Reference List                                                                                               Page 9 AcknowledgmentsMy Dad for buying me my materials that I needed to conduct my trials. Also my Mom for helping me with my test.Purpose and HypothesisPurpose: The purpose with this experiment is to figure out how to use Snell’s law to figure out is the speed of light slows as it travels through substances, such as gelatin. You can measure the speed of light using an inexpensive laser pointer with a protractor and gelatin.Hypothesis: The speed of light will slow down once it passes through the gelatin. I think this because light gets slow down when it enters into denser medium… However, when light travels through a medium that is not empty, the photons interact with the other particles in its way, slowing the photon down. For example, in water, light travels only 0.75c, or 75% the speed of light. This leads me to believe different mediums will slow the speed of light.Review of Literature Snell’s law is used to describe the relationship between angles of refraction and incidence. Snell’s law says that the ratio of the sine thetas of the angles of incidence and refraction are equivalent to the ratio of phase velocities (The phase velocity of a wave is the rate at which the phase of the wave vibrates in space) in the two mediums, or equivalent to the reciprocal of the ratio of the indices of refraction.Application: This can be applied to real life by helping scientists with finding the speed of light easily in different environment.Credit:ScienceBuddies.com Refraction is the bending of a beam of light through a new medium. Snell’s Law is an equation used to find the relationship between the angle of the beam of light before it goes into the medium and the angle of light going through the medium. Sine is the ratio of the line opposite the angle to the hypotenuse(the beam of light). The equation is: n1 *sin(?1 )=n2 *sin(?2 ) . ? n1 = index of refraction of the incident medium ? n2 = index of refraction of the refractive medium ? ?1 = angle of incidence ? ?2 = angle of refraction Background Research (continued) The speed of light in a medium can be calculated using the index of refraction found from Snell’s Law. The equation is v=c/n. ? v = velocity ? c = speed of light in a vacuum ? n = index of refraction for a medium The speed of light in a vacuum 186,282.397 miles per second, the speed of light in air is 186,227.43 miles per second, and the index of refraction of air is 1.000293. Materials and Procedure Materials: -One clear plastic container-Gelatin and other mediums-A protractor -A calculator -A laser Procedure: 1. Take containers and put your medium inside.2. Make sure medium is clear enough.3. Mount the laser and make sure it is stable. 4. Hold one of the containers at a 25° angle beside the laser.5. Turn the laser on and shine it through the medium.6. Use a protractor to measure the angle of refraction when it travels through the substance, the point of incidence (the area in which the light and container meet) being the base point.7. Record observations.8. Repeat steps 3-7 for the other substance.ResultsThe data I got from this experiment shows how fast the speed of light is going after it passes through the gelatin.The angle of entry: 45 degrees The angle of refraction: 31 degrees Refractive Index: 1.373From this data I have collected, I noticed that the speed of light had slowed down. My calculations show that the speed of light has slowed down 173,000,000 mph in gelatin and that means my hypothesis was correct because indeed the speed of light slowed down in gelatin. To find the speed of light through gelatin, you must pass a laser through the clear container filled with clear gelatin, and measure the angle of refraction. For my experiment I set up my container at a 45 degree angle and shined the laser through at that angle as well. When I projected the laser the angle of refraction was 31 degrees. Sin(45)/Sin(31)= .7071/.51501 which then converts to the refraction index which is 1.373Then to find out how fast the speed of light was going through the jello you have to do 1/1.373x(6.71•10 to the power of 8 that then equals 4.89•10 to the power of 8 which equals 498,000,000 mph. My inspiration to do this assignment was because I really wanted to know if you could slow down the speed of light some way. Once you found out what the angle of refraction is for the gelatin you must then figure out the refraction index. To calculate the refraction index you must use the equation above.Conclusion, Reflection, and Application   Conclusion: I conclude that that the speed of light has slowed down 173,000,000 mph in gelatin and that means my hypothesis was correct because indeed the speed of light slowed down in gelatin.  Reflection: I tried my best to get the most accurate results by not moving the container that contained the medium. I can see that their might have been a little bit of human error; For the most part I think I was able to eliminate these by rounding down.Application: This can be applied to real life by helping scientists with finding the speed of light easily in different environments. Such as a vacuum chamber or different gasses.   Reference ListSources: Science Buddies Staff. “Using a Laser to Measure the Speed of Light in Gelatin” Science Buddies. Science Buddies, 28 July 2017. Web. 13 Nov. 2017 Wolfram Research. (n.d.). Snell’s Law. Retrieved July 12, 2010, from http://scienceworld.wolfram.com/physics/SnellsLaw.htmlKaiser, Peter K. (n.d.). Snell’s Law. Retrieved July 12, 2010, from http://www.yorku.ca/eye/snell.htmNave, R. (n.d.). Snell’s Law. Retrieved July 12, 2010, from http://hyperphysics.phy-astr.gsu.edu/hbase/geoopt/refr.html#c3The Physics Classroom. (n.d.). The Mathematics of Refraction: Snell’s Law. Retrieved July 12, 2010, from http://www.physicsclassroom.com/Class/refrn/u14l2b.cfm

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