Plank's Lab
Photoelectric effect
E=hv=KE+W
Equipment
Procedure
We will be following the Gold's Lab manual's expirement for Plank's Constant
Data
Experiment 1 A
White with Yellow Filter:
100% .797V 6.06s
100% .797V 6.34s
100% .797V 6.83s
80% .797V 9.13s
80% .797V 9.22s
80% .797V 9.44s
60% .797V 12.21s
60% .797V 13.28s
60% .797V 11.09s
40% .797V 16.75s
40% .797V 14.88s
40% .797V 15.88s
20% .797V 26.97s
20% .797V 26.09s
20% .797V 29.96s
Green Light Green Filter:
100% .847V 14.16s
100% .847V 13.59s
100% .847V 14.78s
80% .847V 17.75s
80% .847V 18.34s
80% .847V 19.31s
60% .847V 30.07s
60% .847V 27.88s
60% .847V 29.59s
40% .847V 35.41s
40% .847V 35.34s
40% .847V 34.88s
20% .847V 53.28s
20% .847V 61.47s
20% .847V 58.12s
Experiment 1 B
Trial 1 First Order:
Trial 2 First Order:
Trial 1 Second Order:
Trial 2 Second Order:
Second Day Data, Experiment 1 B Cont.
1st order:
Accepted Values
 Work function: 1.36(08)eV
 Plank's Constant: 4.13566733(10)E^15eV*s
Accepted values of Mercury spetra

Yellow

Green

Blue

Violet

UltraViolet

Frequency(Hz)

5.18672E14

5.48996E14

6.87858E14

7.40858E14

8.20264E14

Wavelength(nm)

578

546.074

435.835

404.656

365.483

Sources of Error
 Line Width:The rails that the focusing glass slid along were not long enough to accuratly focus the spectral lines so there is a high possiblity of overlapping spetral lines and or ambient light making it to the aperature thus skewing the data
 Second Order Lines:While taking data we noticed a substantial difference in the stopping potential of the green spretral line between first and second order, we surmised that a possible reason for this would be non visible spetral lines of the first order overlapping the visible green line in the second order. Due to this theory we threw out our second oreder data as possibly corrupt.^{SJK 15:12, 16 November 2008 (EST)}
15:12, 16 November 2008 (EST) yup! take a look at Darrel's lab for how they solved this problem
 Measurement:The measurement of the stopping potential with the multimeter creates the obvious error of slight charge loss durring the measurement due to non infinite resistance in the multimeter, this would be a fairly easy error to correct for by simply knowing the charge loss which I imagine could be found in the multimeter manual.
 Discharge Button:As some cruel joke the makers of this apperatus chose to put the discharge button on the receiver of the light so that it was nearly impossible to push the button without slightly moving the aperture that the light was going through. I definatly think the button should have been attached by a chord to the receiver (like a jeopardy buzzer) (Steve Koch:Ha! Good analogy).
Data Analysis
Analysis performed in Excel, please open attached file to view data analysis
Results
Using the stopping potential averages of all the first order trials and graphing them vs. the frequencies of light associated with those stopping potentials we determined a best fit line whose slope is Planck's constant and whose y intercept is the work function.
 Planck's Constant= 4.54234E15 eV*s with an uncertainty of 5.13689E17 eV*s which when compared to the accepted value of 4.13566733(10)E15 eV*s gave a percent error of 9.38%
 Work Function= 1.63573557 eV with an uncertainty of .034576054 eVwhich when compared to the accepted value of 1.36(08) eV gave a percent error of 20.27%
Summary
Lab Summary
