User:Jason O Archer/Notebook/PHYC 307L Junior Lab/2008/09/29

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Planck's Constant Lab 9/29/08

Notes

SJK 12:33, 20 October 2008 (EDT)
12:33, 20 October 2008 (EDT)good equipment notes
12:33, 20 October 2008 (EDT)
good equipment notes
The list of equipment used is as follows:
  • (1) Pasco Scientific OS-9286 Hg Light Source
  • (1) Pasco Scientific AP-9368 h/e Apparatus
  • (1) Wavetek 85XT True RMS Multimeter
  • (2) Pomona Electronics Banana Cables (model number unknown--not clearly indicated on device)
  • (1) Toppa Stopwatch (model number unknown--not clearly indicated on device)
  • (3) Reflecta transmission filters

The procedures for the lab for today (as well as 2 weeks ago) can be found in Pages 36-45 of this PDF file

Photon Theory of Light, Part A (Continued)

After reconnecting the apparatus as before, I measured the stopping potential for the green line with the green filter at 60% transmission to fluctuate between 0.876 V and 0.877 V. On the first reset, the time to restore was 30.00 sec. On the second reset, the time was 31.97 sec. On the third reset, the time was 33.43 sec.

At this point I noticed the potential briefly rise to 0.878 V. I decided to take this as the new stopping potential (since it was a maximunm, as the others had been). I decided to redo the 60% transmission measurements with this new baseline. Due to time constraints, I will only take three measurements of time in the future, as opposed to five before. Also, the lights had been left on inthe room, possibly skewing the result; the lights are turned off now (they had been off 2 weeks ago). The potential dropped to 0.875 V when the lights turned off, so the results were skewed.

After an accidental reset, the first time at 60% was 36.75 s. The second time was 37.06 s. The third time was 40.19 s. After a reset, @ 40%, the stopping potential was 0.873 V. The first time was 46.50 s. Second time: 47.03 s. Third time: 47.13 s. At 20%, stopping potential = 0.871 V. First time, 91.06 s. Second time, 82.59 s. 3rd time, 99.59 s.

Photon Theory of Light, Part B

Using the first order wavelengths on the right side of the light source, I recorded the stopping potential for each of the five wavelengths of light emitted by the mercury lamp, using yellow and green filters for yellow and green wavelengths, respectively.

First time;
  • For the yellow wavelength with the yellow filter, I measure a stopping potential of 0.752 V with the digital voltmeter (DVM).
  • For the green wavelength with the green filter, I measure a stopping potential of 0.892 V with the DVM.
  • For the blue wavelength, I measure a stopping potential of 1.534 V with the DVM.
  • For the violet wavelength, I measure a stopping potential of 1.735 V with the DVM.
  • For the ultraviolet wavelength, I measure a stopping potential of 2.039 V with the DVM.
Second time;
  • For the yellow wavelength with the yellow filter, I measure a stopping potential of 0.742 V with the DVM.
  • For the green wavelength with the green filter, I measure a stopping potential of 0.879 V with the DVM.
  • For the blue wavelength, I measure a stopping potential of 1.526 V with the DVM.
  • For the violet wavelength, I measure a stopping potential of 1.765 V with the DVM.
  • For the ultraviolet wavelength, I measure a stopping potential fluctuating between 2.061 V and 2.062 V with the DVM.
Third time; (after a reset)
  • For the yellow wavelength with the yellow filter, I measure a stopping potential fluctuating between 0.743 V and 0.744 V with the DVM.
  • For the green wavelength with the green filter, I measure a stopping potential of 0.884 V with the DVM.
  • For the blue wavelength, I measure a stopping potential of 1.517 V with the DVM.
  • For the violet wavelength, I measure a stopping potential of 1.757 V with the DVM.
  • For the ultraviolet wavelength, I measure a stopping potential of 2.070 V with the DVM.

One thing I had noticed during the lab is that whenever my hand got very close to the h/e apparatus, the voltage reading fluctuated wildly.

Determination of h

I took measurements for the second order wavelengths emitted to the right side of the light source.

First time;
  • For the yellow wavelength with the yellow filter, I measure a stopping potential of 0.732 V with the DVM.
  • For the green wavelength with the green filter, I measure a stopping potential of 1.296 V with the DVM.
  • For the blue wavelength, I measure a stopping potential fluctuating between 1.547 V and 1.548 V with the DVM.
  • For the violet wavelength, I measure a stopping potential fluctuating between 1.754 V and 1.755 V with the DVM.
  • For the ultraviolet wavelength, I measure a stopping potential of 2.087 V with the DVM.
Second time;
  • For the yellow wavelength with the yellow filter, I measure a stopping potential of 0.727 V with the DVM.
  • For the green wavelength with the green filter, I measure a stopping potential of 1.282 V with the DVM.
  • For the blue wavelength, I measure a stopping potential of 1.543 V with the DVM.
  • For the violet wavelength, I measure a stopping potential of 1.754 V with the DVM.
  • For the ultraviolet wavelength, I measure a stopping potential of 2.091 V with the DVM.
Third time;
  • For the yellow wavelength with the yellow filter, I measure a stopping potential of 0.733 V with the DVM.
  • For the green wavelength with the green filter, I measure a stopping potential fluctuating between 1.308 V and 1.309 V with the DVM.
  • For the blue wavelength, I measure a stopping potential of 1.540 V with the DVM.
  • For the violet wavelength, I measure a stopping potential of 1.755 V with the DVM.
  • For the ultraviolet wavelength, I measure a stopping potential of 2.094 V with the DVM.


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