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| [[Millikan Oil Drop]]
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| ==Speed of Light Lab Summary==
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| <gallery>
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| Image:Image003.jpg|From left: power supply for photomultiplier, delay box, TAC (time amplitude converter)
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| Image:Image004.jpg|Power supply for LED light emitter.
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| Image:Image005.jpg|oscilloscope
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| Image:Image006.jpg|On top tried different time delay to try and get better signal.
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| </gallery>
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| === Setup ===
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| {{Side comment|comment=[[User:Steven J. Koch|Steven J. Koch]] 01:28, 2 October 2007 (EDT):This is great, adding in model numbers and manufacturers would be excellent}}
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| Start with cardboard tube with photomultiplier in one end and LED emitter in the other.
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| Connect DC power supply (150V-200V) to the LED emitter.
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| Connect BNC cable from the LED emitter to the start in the TAC.
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| Connect DC power supply (1800V-2000V) to the photo multiplier.
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| Connect photo multiplier to the time delay input.
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| Connect from photo multiplier output to stop on the TAC.
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| Connect TAC output to oscilloscope.
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| === Procedure ===
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| We spent the first day setting up the experiment and testing the individual parts to make sure they were working. We were unable to get any data that day but did get some ideas and things to think about for the next week.
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| Before the next Monday we looked at [[Physics307L:People/Ozaksut/Notebook/070912|Anne's Notebook]] and got some ideas from what they did on Wednesday.
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| On Monday we began taking data but noted a problem with the readings we were getting from the scope. We tried switching out the time delay but were still getting the anomalies. Next instead of using a delay we added more BNC cables to create a delay. After this we got better numbers but they were still fluctuating quite a bit.
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| We averaged the oscilloscope and took average readings using the peak output from the photomultiplier (this is achieved by rotating the multiplier to get the right polarization of the light) and averaging the reading from the scope. There were a lot of problems with this method as it was dependent on our ability to correctly turn the multiplier and taking a visual average from the scope. We also tried splitting the output from the multiplier into channel 2 on the scope but still got inconsistent numbers with what was expected.
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| Given these numbers we determined the speed of light to be **2x10^8 m/s (+/- 1x10^8)** as the mean of our readings.
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| ==== Notes and Charts ====
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| [[Physics307L:People/Rivera/Notebook/070917|notebook]]
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| [[image:Speed of light.xls]]
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| === Problems and Issues ===
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| {{Side comment|comment=[[User:Steven J. Koch|Steven J. Koch]] 01:33, 2 October 2007 (EDT):Thank you for all the work you did the first day getting this experiment up and running! Because of that legwork, it looks like Mike is getting some really nice data!}}
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| The first problem we had was the setup. We spent a lot of time trying to locate all the parts need for the experiment. This ended up taking most of the first day.
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| Next it seemed that some of the equipment wasn't working correctly and had to change some of it out and just live with some of it.
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| It also seemed that we were getting some feedback from the LED signal that seemed to be causing the fluctuations in our data. Even with terminators the stream was quite erratic.
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| In averaging the oscilloscope we add in another discrepancy to our data not really knowing how accurate the average is at only 128 cycle averaging. If we could of gotten a reading every tick in a file, and averaged the data ourselves on a spread sheet, I would have felt better about the numbers.{{Side comment|comment=[[User:Steven J. Koch|Steven J. Koch]] 01:33, 2 October 2007 (EDT):Good idea. It turns out that Tomas thinks you are supposed to use the MCA for this experiment. It's not clear to me yet how that works, but if it is able to do the following, it would be like what you're saying, except maybe even better...if it could do this: simultaneously record the pulse height of the PMT and the max of the TAC...then you could manually select out the TAC values when the PMT has the correct pulse height.}}
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| ==Oscilloscope Lab Summary== | | ==Oscilloscope Lab Summary== |
| # Brief summary of what you did (linking to the lab manual page is OK) [http://openwetware.org/wiki/Antonio_C._Rivera_Lab_book/070827# Lab] | | # Brief summary of what you did (linking to the lab manual page is OK) [http://openwetware.org/wiki/Antonio_C._Rivera_Lab_book/070827# Lab] |
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| ''fall time = 57.48ms'' | | ''fall time = 57.48ms'' |
| * Include error bars! | | * Include error bars! |
| {{Side comment|comment=[[User:Steven J. Koch|Steven J. Koch]] 14:33, 28 August 2007 (EDT):I agree: taking multiple measurements and then using Excel or something to compute the mean and standard error of the mean would be a good way to include error bars. If this were a "real lab," I would not accept the answer without error bars, so you would have to find a way to take more data!}}
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| ''should have taken multiple measurements over time the used mean square for value | | ''should have taken multiple measurements over time the used mean square for value |
| and std deviation for error'' | | and std deviation for error'' |
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| ''This was measured by using the oscilloscope's measurement and selecting "fall time"'' | | ''This was measured by using the oscilloscope's measurement and selecting "fall time"'' |
| # What did you learn? | | # What did you learn? |
| {{Side comment|comment=[[User:Steven J. Koch|Steven J. Koch]] 14:36, 28 August 2007 (EDT):I am glad you learned a lot, and that will be great if you can play around with a scope at work. I completely agree that I should have left more time for creative work--I apologize for misjudging how long the exercise would take!<br><br>I will send you an email with your grade for this lab.}}
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| * It's OK if you didn't learn anything. But include things you are still confusing. | | * It's OK if you didn't learn anything. But include things you are still confusing. |
| ''I learned a lot about how to read the scope and to make measurements using the tools on the scope. | | ''I learned a lot about how to read the scope and to make measurements using the tools on the scope. |
