Interferometry lab - Abstract: This experiment makes use of...

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Abstract : This experiment makes use of interferometry to study properties of light. We make use of the nature of waves to study two beams of light, which travel different path lengths, and are then superimposed. The ability to vary path length allows us to alter the position of the wave when superimposed, allowing us to alter the interference pattern created. We can also use polarizers to learn about the interaction of polarized laser beams and therefore the nature of wave propagation. Motivation and Theory : The interferometry experiment uses the interference properties of light to accurately measure the wavelength of a laser, make certain observations about the nature of polarization and observe the coherent properties of a sodium lamp. Laser beams are coherent, which means that all of the waves have been aligned and interfere constructively. When light waves are aligned, their peaks and troughs add and the resulting amplitude is the sum of the individual amplitudes; however, if the waves are not aligned, they interfere and the resulting amplitude is less than the sum. The waves can interfere to the point where the resulting amplitude is zero. This gives us information about the relative positions of the waves. Therefore, two beams of coherent light, split from the same original coherent beam, will create a local maximum of brightness when superimposed if the difference in length traveled is equal to 0 or a multiple of the wavelength. Therefore, if we change the distance traveled by one of the beams and observe how many times the superimposed result changes between maximum and minimum brightness, we can create a relation between path distance and wavelength. Each change from maximum to minimum and back to a maximum corresponds to a change in path length of one wavelength. Because of the apparatus setup, the movement of a mirror by a distance d, results in a path length change of 2d. We therefore relate m, the number of fringes passed, to the distance d by this relation: Apparatus : Interferometer: An interferometer makes use of the coherence of a laser beam by splitting it, with a beam splitter, so that each new beam is reflected back from a mirror. The beams are then superimposed and projected on to a screen. If the two beams traveled the same total
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This document was uploaded on 10/31/2011 for the course PHYSICS 286 at UMass (Amherst).

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Interferometry lab - Abstract: This experiment makes use of...

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