User:Arianna Pregenzer-Wenzler/Notebook/Junior Lab/2008/11/16

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Notes for Formal Report

I am doing my formal report on the Planck's Constant Lab, the purpose of this notebook page is to make a list of areas/ideas that I will need to explore further before my final report is do. I expect I will need to expand my original report in three basic areas;

  • research sources of information, and increase understanding of concepts
  • do a more complet job in the lab
  • refine my data anaylisis techniques

Further Research

  • Classical (wave theory) Rayleigh-Jeans Law
  • Wien's Law
  • Quantum theory (Planck), light is made up of photons (quantized)
  • What is the accepted value for work other in this experiment?
  • Is it just the intensity that decreases for the second order bands?
  • Why was I able to see the green and yellow bands in the second order while the lab manual suggested that these would not be visible (find out where)?


h/e apparatus, PASCO Scientific AP-9368

Hg light source, PASCO Scientific OS-9286

WAVETEK 85XT, multimeter

Tektronix TDS 1002 , two channel digital storage oscilloscope

– h/e Apparatus, (AP-9368*) – h/e Apparatus Accessory Kit, (AP-9369*) – Mercury Vapor Light Source, (OS- 9286*)

Back in the Lab


  • Today I am seeing a red band after the yellow band, I will note its stoping potential (if any)
  • I am going to take green and yellow voltage using the yellow filter for green and my rayban polarized sunglasses because they seem to have a good UV filter along with the yellow filter for yellow
Spectral band Voltage (V)(1st order) error Voltage(V)(2nd order) error
UV 2.033 .0005 2.034 .0005
Blue I 1.698 .001 1.707 .001
Blue II 1.478 .0005 1.571 .001
Green 0.820 .0005 0.841 .002
Yellow .695 .002 0.829 .002

In the end for the second order green I used the yellow and the green filter and my sunglasses, for yellow I used just yellow filter and my sunglasses. It does seem that I am able to better my second order results by trying to filter overlap from higher order bands. My voltages continue to creep up so I could be showing the fact that a decrease in intensity does indeed led to a measurable (by stopwatch) change in charging time, or, more likely I am highlighting other systematic error in the apparatus.

Spectral band Voltage (1st order) error Voltage (2nd order) error
UV 2.044 .001 2.033 .001
Blue I 1.676 .0005 1.716 .001
Blue II 1.485 .0005 1.547 .0005
Green 0.845 .0005 0.860 .002
Yellow 0.719 .000 0.730 .001

I was really careful with this second run to make sure the spectral beam was directly aligned with the photo diode. I used the yellow filter with the yellow band and the green filter with green first order. Second order I used green and my sunglasses for green and yellow green and my shades of yellow. There is enough interference from higher bands with these two bands to make me think that this data should be excluded from the final results. The other option would be to weight it less (use a weighted average to calculate my best guess).

Data Anaylisis

  • Why does the value of work other increase for the second order lines? Sould I weight 2nd order terms differently, look at time vs stoping potential on the oscilliscope for 1st vs 2nd order.
  • look again at formula for weighted averages, find out how to calculate a weighted error(done)