Physics307L:People/Muehlmeyer/Formal: Difference between revisions
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==Abstract== | ==Abstract== | ||
To approximate the speed of light we measured the "flight time" of pulses of light emitted by a light emitting diode by measuring the time difference between LED emission and PMT reception of the light signal down a tube via a time amplitude convertor (TAC). By varying the distance the light signal travels we plot distance vs. flight time and use the linear-least squares method to approximate the slope of our data, which gives us the speed of light. We found that our best approximation to the accepted value of 2.99 X 10<sup>8</sup> was 2.94 X 10<sup>8</sup> m/s, which came from large variations in distance and from using the "time walk" correction that accounts for the changing intensity of the light as the LED distance approaches the PMT. | To approximate the speed of light we measured the "flight time" of pulses of light emitted by a light emitting diode by measuring the time difference between LED emission and PMT reception of the light signal down a tube via a time amplitude convertor (TAC). By varying the distance the light signal travels we plot distance vs. flight time and use the linear-least squares method to approximate the slope of our data, which gives us the speed of light. We found that our best approximation to the accepted value of ''2.99 X 10<sup>8</sup> m/s'' was ''2.94 X 10<sup>8</sup> m/s'', which came from large variations in distance and from using the "time walk" correction that accounts for the changing intensity of the light as the LED distance approaches the PMT. | ||
==Introduction== | ==Introduction== |
Revision as of 11:27, 16 November 2008
Measuring the Speed of Light
Author: Justin Muehlmeyer
Experimentalists: Justin Muehlmeyer and Alexander Barron
University of New Mexico
Department of Physics and Astronomy Junior Lab November 2008
jmuehlme@unm.edu
Abstract
To approximate the speed of light we measured the "flight time" of pulses of light emitted by a light emitting diode by measuring the time difference between LED emission and PMT reception of the light signal down a tube via a time amplitude convertor (TAC). By varying the distance the light signal travels we plot distance vs. flight time and use the linear-least squares method to approximate the slope of our data, which gives us the speed of light. We found that our best approximation to the accepted value of 2.99 X 108 m/s was 2.94 X 108 m/s, which came from large variations in distance and from using the "time walk" correction that accounts for the changing intensity of the light as the LED distance approaches the PMT.