lab 5 refraction reflectoin

# lab 5 refraction reflectoin - Reflection, Refraction and...

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Reflection, Refraction and Polarization Lab Suneet Bhansali February 24, 2010 TA: Ryan Partners: Carolina, Logan, and Trey Phys 105 – Section 413 Pledge __________________________________________

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Abstract: In this lab we investigated the refraction and reflection by experimentally determining the index of refraction for an acrylic solid. In each part of the experiment, we aimed a He-Ne laser beam through a semi-circular acrylic disk, placed on top of a ray table base. In part 1, the index of refraction was found using Snell’s law. We then compared the angle of refraction to the angle of incidence and got in index of refraction of 1.467±.01. In part 2, we used the critical angle, the angle at which the refracted ray disappears, to calculate an index of refraction of 1.47±06. Finally, in part 3 we used Brewster’s angle, the angle at which the refracted and reflected rays are at 90º to calculate an index of refraction of 1.54±0.2. Parts 2 and 3 agreed with the accepted value of 1.49, but the index of refraction determined in part 1 did not agree with this accepted value. This discrepancy may be due to the fact that the acrylic disk moved while rotating the base table, thus providing inaccurate data. Introduction In this lab, we used a laser beam and an acrylic solid to determine the index of refraction for the solid. The idea behind this lab is that a transparent object can split light beams by reflecting some parts of the beam and allow others to pass through. In previous experiments, it has been shown that the angle of reflected light is equal to the angle of the incident light. When we pass a beam through the solid, the transmitted ray is bent, or refracted, and the angle of the bent beam is related to the angle of the incident ray by Snell’s Law: n 1 sin( Ө 1 )=n 2 sin( Ө 2 ), where n 1 and n 2 are the index of refraction of mediums 1 and 2. The index of refraction is the ration of the speed of light in vacuum to the speed of light in the material, n=c/v. In the second part of the experiment, we learned that if the angle of incidence is greater than the critical angle, light cannot pass from a solid, which has a higher index of refraction, to
air, which has a lower index of refraction. In other words, if light passes from one medium to another with a smaller index of refraction, the angle of refraction should be higher than the angle of incidence. Ideally, the angle of refraction should be 90º at the critical angle of incidence. At this angle, the transmitted light will not directly enter the second medium, but will instead travel along the boundary of the two media. If the incident angle is greater than the critical angle, the light will reflect back into the solid. To test this theory, we used the equation sin(

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## This note was uploaded on 11/27/2011 for the course PHYS 105 taught by Professor Walker during the Fall '08 term at UNC.

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lab 5 refraction reflectoin - Reflection, Refraction and...

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