Experiment 5 - Polarization and Interference

Experiment 5 - Polarization and Interference - Eric Chong...

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Eric Chong PHYS C1493 Partner: Albert Lee Lab Date: October 19, 2006 Experiment 5: Polarization and Interference Introduction This lab investigates two basic concepts of wave mechanics, that of the polarization of light and of interference. Using an incandescent light to generate a source of unpolarized light, we use a photometer to measure the declining intensities of the light as we vary the angle of the polarizer through which the light source enters. We do this to test the validity of Malus’ Law, given by the equation: 2 0 cos I I θ = , which suggests that the intensity ratio plotted against the square of the cosine of the angle of the polarizer should give a straight line. The second procedure of the lab incorporated the concepts of constructive and destructive interference, where by using a double slitted filter we can find the maxima and the minima of the intensity produced by a beam of light of wavelength λ dependant upon the distance between the slits d and the distance from the light source to the viewing screen, D . These are related by the equation: m D x m d λ = , where x m is the diffraction maxima length. The points at which intensity is the highest are points at which constructive interference of the two paths of light are fully in effect. These points, and knowledge of the length x from the central maximum, allow us to calculate the wavelength of the light which is a inert characteristic of the light itself. Procedure The initial set up of the lab required a light source, two polarizers (to calculate the difference in angle, θ between them) a linear translator to hold the fiber optic cable which was connected to the photometer to gauge the intensity of light. The linear translator was set up in its middle position to most accurately gauge the intensity of light. In theory, as the angle difference θ between the polarizers approaches 90°, decreasing amounts of light should pass through and the intensity recorded by the photometer should approach zero. 19 trials were taken in increments of 5°, including one trial for I 0 , which was the intensity measurement for 0° difference between the polarizing axes. The second procedure required the use of a laser (a form of
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This note was uploaded on 12/16/2010 for the course PHYS 1493 taught by Professor Lab during the Spring '08 term at Columbia.

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Experiment 5 - Polarization and Interference - Eric Chong...

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