Physics307L F07:People/Joseph/Lab5

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Speed of Light

My final value for the speed of light was c = 3.164 * 109m/s with an uncertainty of pm.0001 / times109 m/s. My value was about 5% off of the accepted value, and my data and calculations can be found here SJK 01:30, 9 December 2007 (CST)
01:30, 9 December 2007 (CST)I don't think you converted the error correctly.  The % error in the MCA values should be same after converting to m/s
01:30, 9 December 2007 (CST)
I don't think you converted the error correctly. The % error in the MCA values should be same after converting to m/s

Our error was likely from our uncertainty in whether or not the PMT was consistently recieving the same amount of light, and this uncertainty would be propagated throughout the rest of the experiment. It would be a good idea to have the PMT fixed and have the polarizer mounted in some sort of a ring that you'd be able to manipulate from outside the tube. If you had a oscilloscope right with you, one with a very high resolution, you could cut this error down dramatically.

It would not have been a bad idea to make a schematic of how everything is plugged, people seemed to have trouble making this experiment easily repeatable.SJK 01:33, 9 December 2007 (CST)
01:33, 9 December 2007 (CST)That is a good idea for being able to rotate the polarizer w/o moving the PMT.  You may be able to implement it with rare earth magnets cheaply, or with a motorized polarizer more expensively.  Another idea Tomas had for adjusting the PMT level by tweaking the HV power supply.  I don't know yet how well that turned out.  As for better instructions, I'm sort of now liking that there were a lot of struggles that students had to go through on these labs. That is a great way to learn about research!
01:33, 9 December 2007 (CST)
That is a good idea for being able to rotate the polarizer w/o moving the PMT. You may be able to implement it with rare earth magnets cheaply, or with a motorized polarizer more expensively. Another idea Tomas had for adjusting the PMT level by tweaking the HV power supply. I don't know yet how well that turned out. As for better instructions, I'm sort of now liking that there were a lot of struggles that students had to go through on these labs. That is a great way to learn about research!

This lab could use some improvement, and Bradley and I had to do some acrobatic solo flying on this one, but I learned a lot and it was interesting to see how one would measure something like the speed of light.

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