Refraction in LiquidsPhysicsExperimental Investigation___________________________________________Signature of Sponsoring Teacher___________________________________________Signature of School Science Fair Coordinator TeacherBailey Zalewski640 W.
Scott St. Chicago, IL 60610Grade #8Table of ContentsAcknowledgments Page 3Purpose and Hypothesis Page 4Background Research Page 5Materials and Procedure Page 9Results Page 13Conclusion, Reflection, Application Page 15Reference List Page 17Acknowledgments I would like to thank my Mom for helping me with measurements and getting all of my supplies. I would also like to thank Science Buddies for suggesting the materials I needed for this experiment. Without my Mom or Science Buddies, I would not have been able to do this project well. Purpose and HypothesisMy purpose in this experiment was to figure out which of my liquids had the largest index of refraction and angle of minimum deviation. The liquids I used were water, sugar water, ginger ale, Gatorade, Sprite, and Sprite Zero. I did this by calculating how far the light of a laser was bent as it passed through my liquids. I hypothesized that if a liquid was more opaque then the laser would have a harder time passing through and creating angles because opaque liquids absorb light.
Review of LiteratureRefraction is the bending of a wave as it passes from one material into another. The amount of refraction, or how much a light wave bends when it travels from one medium to another, is related to the indices of refraction by a mathematical formula called Snell’s Law (https://www.sciencebuddies.org/science-fair-projects/project-ideas/Phys_p028/physics/measuring-sugar-content-of-a-liquid-with-a-laser-pointer#background). Snell’s Law describes the relationship between the angles and the velocities of the waves. Snell’s law equates the ratio of material velocities V1 and V2 to the ratio of the sine’s of incident (Q1) and refracted (Q2) angles (https://www.nde-ed.
org/EducationResources/CommunityCollege/Ultrasonics/Physics/refractionsnells.htm). The more that light refracts, the bigger the difference between these two angles (http://www.
physicsclassroom.com/class/refrn/Lesson-2/Snell-s-Law). Different terms that were used through this experiment were angle of minimum deviation, refraction, index of refraction, Snell’s law, angle of incidence, angle of refraction, density, and prism. Angle of minimum deviation means: a ray of light is deflected twice in a prism. Refraction means: the change of direction of a ray of light, sound, heat, or the like, in passing obliquely from one medium into another in which its wave velocity is different. Index of refraction means: a number indicating the speed of light in a given medium as either the ratio of the speed of light in a vacuum to that in the given medium (absolute index of refraction) or the ratio of the speed of light in a specified medium to that in the given medium (relative index of refraction).
Snell’s law states: for a ray incident on the interface of two media, the sine of the angle of incidence times the index of refraction of the first medium is equal to the sine of the angle of refraction times the index of refraction of the second medium. Angle of incidence means: the angle that a straight line,ray of light, etc., meeting a surface, makes with a normal to the surface at the point of meeting. Angle of refraction means: the angle between a refracted ray and a line drawn normal to the interface between two media at the point of refraction. Density means: the state or quality of being dense; compactness; closely set overcrowded condition.
Finally, prism means: a transparent solid body, often having triangular bases, used for dispersing light into a spectrum or for reflecting rays of light (http://www.dictionary.com).
Greek mathematician Archimedes was the one who first discovered the idea of density when he got into a pool and noticed that water spilled out of the top when he got in. Density is a physical property of matter that expresses a relationship of mass to volume. The more mass an object contains in a given space, the more dense it is. It is important to remember, though, that this relationship is not just about how closely packed together the atoms of an element or the molecules of a compound are. Density is also affected by the atomic mass of an element or compound. Since different substances have different densities, density measurements are a useful means for identifying substances.
Density can sometimes be confused in our minds with weight because the denser of two equal-volume objects will be heavier (https://www.visionlearning.com/en/library/General-Science/3/Density/37).
Prism, in optics, is piece of glass or other transparent material cut with precise angles and plane faces, useful for analyzing and reflecting light. An ordinary triangular prism can separate white light into its constituent colours, called a spectrum. Each colour, or wavelength, making up the white light is bent, or refracted, a different amount; the shorter wavelengths (those toward the violet end of the spectrum) are bent the most, and the longer wavelengths (those toward the red end of the spectrum) are bent the least. Prisms can reverse the direction of light by internal reflection, and for this purpose they are useful in binoculars. Prisms are made in many different forms and shapes, depending on the application (https://www.britannica.
com/technology/prism-optics). When white light shines through a prism, each colour refracts at a slightly different angle. Violet light refracts slightly more than red light. A prism can be used to show the seven colours of the spectrum that make up white light (https://www.
sciencelearn.org.nz/resources/49-refraction-of-light). Theodore Maiman developed the first working laser at Hughes Research Lab in 1960.
Maiman’s early laser used a powerful energy source to excite atoms in a synthetic ruby to higher energy levels. At a specific energy level, some atoms emitted particles of light called photons. The new photons struck other atoms, rapidly stimulating the emission of more identical and amplifying the light intensity. Maiman continued the process of stimulated emission and amplification by placing a completely silver mirror on one end of the model and a partially reflecting silver mirror on the other. This setup enabled photons to bounce back and forth between the mirrors until they gained enough intensity to burst through the partially end as a powerful, coherent, beam of light.
Laser is an acronym for Light Amplification by Stimulated Emission of Radiation (http://laserfest.org/lasers/history/early.cfm). Some other pieces of information found are different materials have different optical densities. The optical density of a material tells us how fast light can travel through it. Light and other waves travel through a medium (http://web.mit.edu/knazemi/www/advancedExperiment1.
htm). This bending by refraction makes it possible for us to have lenses, magnifying glasses, prisms and rainbows. Even our eyes depend upon this bending of light. Without refraction, we wouldn’t be able to focus light onto our retina.
When light travels from air into water, it slows down, causing it to continue to travel at a different angle or direction. The amount of bending depends on two things: Change in speed – if a substance causes the light to speed up or slow down more, it will refract (bend) more. As well as the angle of the incident ray – if the light is entering the substance at a greater angle, the amount of refraction will also be more noticeable. On the other hand, if the light is entering the new substance from straight on (at 90° to the surface), the light will still slow down, but it won’t change direction at all. If light enters any substance with a higher refractive index (such as from air into glass) it slows down. The light bends towards the normal line. If light travels enters into a substance with a lower refractive index (such as from water into air) it speeds up. The light bends away from the normal line.
A higher refractive index shows that light will slow down and change direction more as it enters the substance. Clear liquids are more transparent and light will be able to pass through it easier (https://www.sciencelearn.org.nz/resources/49-refraction-of-light).
Materials and ProcedureMaterials:Hollow acrylic prism Stopper for prismSmall funnelLaserCardboardMasking tapeTape measure/rulerString 1.2 metersPencilPaper (17×34) and (8×11)1.05 grams of sugar22 mL of water22mL of Ginger Ale22 mL of Sprite22 mL of Diet Sprite22 mL of Glacier Cherry GatoradeCalculator with trigonometric functions ( eclac.com ) Procedure:Find an open space with a wall and table to set up the experiment Set up your materials in this format 3.
Put the laser pointer on a table. The laser’s beam should be perpendicular to the wall (red dotted line) 4. The 17 inch by 34 inch piece of paper should be taped to the wall 5. Lay the 8 by 11 inch paper in front of the laser pointer. This will be used to mark where the laser beam enters and exits the prism 6.
Place the prism on the 8×11 paper a few centimeters in front of the laser pointer 7. Use the pencil to trace the base of the prism. If you move it, return it to the traced spot 8. Adjust the height of the laser with cardboard until the laser’s beam hits about halfway up the side of the prism 9. Tape the laser to the cardboard it’s on and then tape the cardboard to the table so that it doesn’t move. If it moves, results will not be accurate 10.
Tape the 17×34 piece of paper to the wall to measure where the laser beam hits the wall 11. When the laser is completely empty, turn the laser on and mark the place where beam hits the paper taped to the wall. Make this point b 12. With the prism empty, mark where the beam enters the prism and mark it point d 13.
With the prism still empty, mark where the laser beam exits the prism and mark it point e 14. Turn the prism so the path of the refracted beam in the prism is parallel with the base of the prism, the side of the prism that has no laser beam hitting it 15. When the prism is turned correctly, mark where the beam hits the paper taped on the wall. Label this point a 16. On the piece of paper on the table, mark where the beam emerges from the prism.
Label this point f 17. Set the prism to the side while you measure and draw lines. 18. Use a ruler or tape to draw a line from point e to d. This marks the path of the undiverted beam 19. Then extend a line from point a through point f.
Do this by stretching the string from point a so that it passes over point f. Mark where the string and line ed intercept point c 20. Measure the distance from point a to point b and record it in the table. This is distance x 21.
Measure the distance from point b to point c and record it in the table. This is distance L 22. The distances measured can calculate the angle of minimum deviation by dividing x/L. You can do this by going to eclac.com.
Record this in the table 23. Now you can evaluate the index of refraction by using the equation: n= 2.00056 • sin0.5(angle of minimum deviation + 60°) 24. Record that in the table 25. Repeat steps 11-24 for each liquid substance and record it in the tableResultsLiquidDistance from point a to point b (centimeters)Distance from point b to point c(centimeters)Angle of minimum deviation(degrees)Index of Refraction(degrees)Empty0 centimetersN/A0 degrees-198 degreesWater35.
56 centimeters66.04 centimeters53.84 degrees73 degreesSugar Water34.29 centimeters68.58 centimeters50 degrees-200 degreesGinger Ale44.
45 centimeters66.04 centimeters67.30 degrees146 degreesGatorade45.085 centimeters69.85 centimeters64.54 degrees-107 degreesSprite36.
195 centimeters67.31 centimeters53.77 degrees66 degreesSprite Zero41.91 centimeters69.215 centimeters60.55 degrees-110 degrees This table is showing the different measurements I took with the different liquids, plus the empty prism. The different measurements include the distance from point a to point b, the distance from point b to point c, angle of minimum deviation, and the index of refraction. The measurements from point a to point b for each liquid are: 0 centimeters (empty), 35.
56 centimeters (water), 34.29 centimeters (sugar water), 44.45 centimeters (ginger ale), 45.
085 centimeters (Gatorade), 36.195 centimeters (Sprite), and 41.91 centimeters (Sprite Zero).
The measurements from point b to point c for each liquid are: N/A (empty), 66.04 centimeters (water), 68.58 centimeters (sugar water), 66.
04 centimeters (ginger ale), 69.85 centimeters (Gatorade), 67.31 centimeters (Sprite), and 69.125centimeters (Sprite Zero). The measurements for angle of minimum deviation are: 0 degrees (empty), 53.84 degrees (water), 50 degrees (sugar water), 67.
30 degrees (ginger ale), 64.54 degrees (gatorade), 53.77 degrees (sprite), and 60.
55 degrees (sprite zero). The measurements for the index of refraction are: -198 degrees (empty), 73 degrees (water), -200 degrees (sugar water), 146 degrees (ginger ale), -107 degrees (gatorade), 66 degrees (sprite), and -110 degrees (sprite zero).Conclusion, Reflection, and ApplicationConclusion:My science fair project is about measuring the index of refraction in different types of liquids. I wanted to find out which of my liquids: water, sugar water, ginger ale, Gatorade, Sprite, and Sprite Zero, had a larger index of refraction and angle of minimum deviation. I hypothesized that if a liquid was more opaque then the laser would have a harder time passing through and creating angles because opaque liquids absorb light.
I tested this by using a prism, which bends light, and a laser pointer. I followed my procedure for each liquid and calculated everything needed. I noticed that the fizzier drinks had larger measurements. Also, something I noticed and found intriguing was that Sprite was a lot lower in all the categories next to all the other sodas. I expected it to be fairly close to the other sodas. I measured that ginger ale has the highest angle of minimum deviation and that sugar water has the lowest angle of minimum deviation. Another thing I noticed was that when I was calculating the index of refraction, I got negative angles. That could have happened from human error or maybe the equation I used only works for certain numbers.
My hypothesis was proven incorrect. I know my hypothesis was incorrect because the laser was able to pass through all the liquids. I had thought that the laser wouldn’t be able to pass through liquids like Gatorade and ginger ale. I learned that fizzier drinks will most likely have a larger angle of minimum deviation.Reflection:All of my tests were fair because I did the same thing to each test and didn’t give any substance/test special treatment. I think my results were accurate because I followed my procedure accurately and made sure each step was completed properly. I wouldn’t really change the experiment because everything was done well and I feel that I got accurate results. Some things I would want to do to further this experiment would be to add some more liquids to the selection.
Some things I’m curious about are how would the intensity of the laser effect the final results and how would different distances affect the results.Application: This experiment can be used in a real life situation because it helps explain a rainbow. The sunlight is refracted through raindrops and creates the different bursts of light. The results of my experiment are important to the field of science because it shows the behavior of light.
It show what light does when it goes through an empty prism compared to when it passes through a prism with liquid inside of it. This experiment connects to our everyday lives because there is refraction everywhere. Some examples are a straw in water; when it appears to be bending, when a person is in a pool and their legs appear to be oddly small, and rainbows. My experiment explains why things appear to be bent when they are in a liquid substance.Reference ListDay, M.
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(1998, July 20). Prism-Optics. Retrieved November 19, 2017, from https://www.britannica.
com/technology/prism-opticsLaser Fest. (n.d.). Early history.
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