User:Alex G. Benedict/Notebook/Physics 307L: Junior Lab/Speed of Light
Speed of Light Lab Summary
Summary of ActivitiesSJK 21:37, 25 October 2010 (EDT)User:Alex_G._Benedict/Notebook/Physics_307L:_Junior_Lab/Speed_of_Light_Lab. We took data for the speed of light using two different techniques, one where the distance of the LED from the PMT mattered, and one where that could be arbitrary. To measure the time it took light to traverse some distance we measured the peak to peak voltages of a waveform on the oscilloscope, and converted the voltages to nanoseconds using the values given by Joesy and Harriger of 1V=10ns. The units from the first day of data measurement are volts and meters. For the second day the units are 0.1 voltsSJK 21:35, 25 October 2010 (EDT)
For the first day:
The slope of the line in the picture is 0.20079999999999 +/- 0.1258206130436 which actually contains the speed of light(about 0.3 in those units) within the uncertainty. So we known with about 68% confidence that the speed of light is in the interval [7.4,32.59] cm/ns.
For the second day:
The average slope for the data was -3.26848484848484 +/- 0.24476146068253, where the uncertainty is taken to be the maximum of the the uncertainties of each fit. The minus sign is irrelevant and comes from the fact that the distance from the LED to the PMT was decreasing, so with 68% confidence we know the speed of light is within the interval [30.24,35.13] cm/ns.
A sample plot from this day is given below for trial 8(this was a particularly good trial):