User:Manuel Franco Jr./Notebook/Physics Lab 307/2008/09/17: Difference between revisions
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==Data Analysis== | ==Data Analysis== | ||
All my data is in this spread sheet: ( ). I followed Jessy's format to plot | All my data is in this spread sheet: ( ). I followed Jessy's format to plot and analyze my data. My Slope, or measurement for the speed of light is 352261684.3 m/s. | ||
==Lab Summary== | ==Lab Summary== | ||
Revision as of 15:09, 30 September 2008
 Speed of Light Lab
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Measuring the Speed of LightLab Partner: David ObjectiveThe objective is in the title. We are going to measures the speed of light using such materials, and follow a certain procedure as described below. Equipment
Here are some photos of the equipment used:
ConnectionsWhen we arrived everything was already setup by the Lab prior to us, but we still had to review the equipment and wires to check if they were in the correct place. We were aided by Koch, but also by the Lab Manual, Section 10. At this point everything is turned off, and all the dials are set to there lowest settings. The TAC, the delay, and the power supply {1} were in the NIM bin. The second power supply {2} was connected to LED. The LED was taped to a meter stick which was taped to another meter stick. It was inserted into the cardboard tube on one end. The LED was contected to the TAC's "start." As for the other end, the PMT was inserted there. The Lab manual warns, and I quote, "Warning! This experiment uses a photomultiplier tube (PMT) that will be ruined if exposed to ambient light when at operating voltages. Please be careful - the PMT must never be exposed to any bright light source while its high voltage is turned on. Permanent damage will result!" Lab Manual, Section 10.2. The PMT has three connections, and we connected the following. The PS{1} was connected to the PMT. Then, the PMTs second connection was connected to the delay. From the delay it was connected to the "stop" input of the TAC, and then from the TAC output into the DSO in channel two. As for the third connection it was connected to channel one in the DSO. So, everything was correctly connected, now we were able to turn on all the instruments, and begin gathering data. ProcedureAfter checking if everything was set up correctly, we turned on the TAC, both power supplies, and the DSO. So as instructed by the Lab manual we set the PS{1} to about 1800 V to 2000 V. We decide set PS{1} at 1990 V, and PS{2} to 150 V to see if we were getting any data at all. Nothing... With help from Koch, we figured out that the PS{2} was set low, and that our DSO was out of range. So we set PS{2} to 170 V (+/- 1 V), and ranged the DSO. Finally, we obtained the two graphs necessary to record data, as shown in Photo 2. Time walk is a new time that I became familiar with in this experiment. The speed of light travels approximately a foot per nanosecond; so the instant we turned on the equipment and the LED emitted that pulse, light had to travel several feet to light up the LED. That delay in light would ruin our measurements. The delay would help us make a reference to how light was moving. As for the TAC, it had to be trigger at a fixed voltage due to the polarization in the PMT and LED. The lab manual goes more in to detail over this process. As we moved the LED and PMT we change the distance between them, and we measured the voltage in which we get the time from that. Whether if we bring the LED closer to the PMT, or if we pull the LED away from the PMT the speed of light is constant. With this data we can make distance and time graph. With that we can obtain a slope or velocity, hence our measurement of the speed of light. DataPS{1}: 1908 V (-/+ 1 V) on all measurements PS{2}: 170 V (-/+ 1 V) on all measurements 1st MeasurementPMT Reference Voltage: -648mV (-/+ 1 V)? Range (TAC): 50 ns Time delay: 0 nsecs 1.) 150 cm 2.56 V 2.) 140 cm 3.48 V 3.) 120 cm 3.68 V 4.) 100 cm 3.36 V 5.) 80 cm 3.12 V 6.) 60 cm 2.69 V 7.) 50 cm 2.12 V 2nd MeasurmentPMT Reference Voltage: -1.12V (-/+ 1 V) Range (TAC): 50 ns Time delay: 0 nsecs 1.) 60 cm 2.10 V (+/- 0.04 V) 2.) 50 cm 2.04 V (+/- 0.04 V) 3.) 40 cm 2.02 V (+/- 0.04 V) 4.) 30 cm Same as above 5.) 20 cm 1.95 V (+/- 0.04 V) 6.) 10 cm 1.84 V (+/- 0.04 V) 3rd MeasurmentPS{1}: 1908 V (-/+ 1 V) PMT Reference Voltage: 850 mV(-/+ 1 V)? Range(TAC): 50 ns Time delay: 0 nsecs 1.) 160 cm 3.00 V (-/+ 0.04 V) 2.) 150 cm 2.94 V (-/+ 0.04 V) 3.) 140 cm 2.90 V (-/+ 0.04 V) 4.) 130 cm 2.87 V (-/+ 0.04 V) 5.) 120 cm 2.82 V (-/+ 0.04 V) 6.) 110 cm 2.78 V (-/+ 0.04 V) 7.) 100 cm 2.70 V (-/+ 0.04 V) 8.) 90 cm 2.66 V (-/+ 0.04 V) 9.) 80 cm 2.54 V (-/+ 0.04 V) 10.) 70 cm 2.52 V (-/+ 0.04 V) 11.) 60 cm 2.46 V (-/+ 0.04 V) 12.) 50 cm 2.38 V (-/+ 0.04 V) 4th MeasurmentMeasurments with time delay PS{1}: 1900 V (+/- 1 V) PMT Reference Voltage: 1.2 V Range (TAC): 50 ns Time Delay: 2 nsecs 1)130 cm 2.38 V (-/+ 0.04 V) 2)120 cm 2.34 V (-/+ 0.04 V) 3)110 cm 2.22 V (-/+ 0.04 V) 4)100 cm 2.14 V (-/+ 0.04 V) 5)80 cm 2.04 V (-/+ 0.04 V) Data AnalysisAll my data is in this spread sheet: ( ). I followed Jessy's format to plot and analyze my data. My Slope, or measurement for the speed of light is 352261684.3 m/s. Lab SummaryReferences | |
![Photo 6: PS{1} for the PMT (left), delay module(center), and the TAC (right).[1]](/wiki/File:Physics_307L_Speed_of_light1.JPG)
