Calculating the Speed of Light

PIXE-PAN 2007: Calculating the Speed of Light

PIXE-PAN 2007: Calculating the Speed of Light

By: Annie Sauer, Caitlyn Koscielski, and Gary Brizendine II

Advisor: Mark Mankowski

By: Annie Sauer, Caitlyn Koscielski, and Gary Brizendine II

Advisor: Mark Mankowski

Purpose of the ExperimentPurpose of the ExperimentDetermine the speed of light using gamma ray emissionLearning how to analyze extremely rapid events using precise equipment

Determine the speed of light using gamma ray emissionLearning how to analyze extremely rapid events using precise equipment

Experimental SetupExperimental SetupTrack with two sensors at each endSource between the two sensors which emits gamma rays into them

Track with two sensors at each endSource between the two sensors which emits gamma rays into them

ProcedureProcedure1. Calibrate apparatus using start sensor2. Collect data pertaining to the different delay

increments while calibrating3. Once calibration is finished, set up source so its

distance from each sensor is equal (make this appear as the midpoint on the computer)

4. Select several different points to obtain data

1. Calibrate apparatus using start sensor2. Collect data pertaining to the different delay

increments while calibrating3. Once calibration is finished, set up source so its

distance from each sensor is equal (make this appear as the midpoint on the computer)

4. Select several different points to obtain data

CalibrationCalibrationTo ensure accuracy, calibrating the detectors was the first step

To ensure accuracy, calibrating the detectors was the first step

153847

124640

99234

75428

50722

Channel #Delay (nS)

Calibration Data

y = 0.0242x + 4.3639

0

5

10

15

20

25

30

35

40

45

50

0 200 400 600 800 1000 1200 1400 1600 1800Channel Number

Collecting DataCollecting DataUse the difference in the times and distances traveled by the rays to determine the speed of lightMove the source relative to the detectors

Use the difference in the times and distances traveled by the rays to determine the speed of lightMove the source relative to the detectors

How It WorksHow It WorksThe source (sodium-22) emits a positron that annihilates an electron in its path, releasing two photons that have 511 keVThe detectors pick up the photons and sends an analog signal to a converterThe converter sends a digital signal to the computerThe computer records the delay from each sensor (start and stop sensors)The peak of each signal is determined and recorded as data

The source (sodium-22) emits a positron that annihilates an electron in its path, releasing two photons that have 511 keVThe detectors pick up the photons and sends an analog signal to a converterThe converter sends a digital signal to the computerThe computer records the delay from each sensor (start and stop sensors)The peak of each signal is determined and recorded as data

Analysis Analysis After recording the data, it is transferred to a table in excelUse the table to make graphs of the dataCreate the trend-line of the graphsTwo graphs: one for the calibration data and one for the experiment dataUse the slopes of the two graphs to find the speed of light

After recording the data, it is transferred to a table in excelUse the table to make graphs of the dataCreate the trend-line of the graphsTwo graphs: one for the calibration data and one for the experiment dataUse the slopes of the two graphs to find the speed of light

The ResultsThe Results

27.4727-220 cm

30.1838-110 cm

32.1921-80 cm

34.910350 cm (center)

37.5114580 cm

39.61229140 cm

42.31342220 cm

Time (nS)

Channel Number

Path Difference

Speed of light

y = 0.7158x - 748.6

-250

-200

-150

-100

-50

0

50

100

150

200

250

0 200 400 600 800 1000 1200 1400

Channel Number

Error in the ExperimentError in the ExperimentMeasured speed: 2.95 x 108 m/sAccepted speed: 2.99 x 108 m/sPercent Error: 1.34%

Measured speed: 2.95 x 108 m/sAccepted speed: 2.99 x 108 m/sPercent Error: 1.34%

Picture: http://www.webdesign.org/img_articles/239/step_5.jpg

PIXEPIXEThree different penniesThree different pennies

Penny One: 1941Penny One: 1941

Mainly composed of copper Also found zinc

Mainly composed of copper Also found zinc

Penny Two: 1943Penny Two: 1943

Steel penny: had mostly iron and zincReason for this change: the copper was needed for the war effort

Steel penny: had mostly iron and zincReason for this change: the copper was needed for the war effort

Penny Three: 2007Penny Three: 2007

Composed of mainly zinc (the core)Copper coatingReason for this change: rising cost of copper

Composed of mainly zinc (the core)Copper coatingReason for this change: rising cost of copper