User:Alex G. Benedict/Notebook/Physics 307L: Junior Lab/Planck's Constant Lab

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Steve Koch 04:28, 21 December 2010 (EST):Again, more detail is necessary to enable reproducibility. Also, we did not get to discuss issues with the 2nd order green band, which I apologize for.


Balmer Series Lab

This lab was performed in the junior laboratory in the UNM physics building on November 29, 2010.


[Dr. Gold's Lab Manual]

Equipment and Setup

Mercury Vapor Light Source and Light Block(Model OS-9286)
  • Voltage Range: 108-132 VAC
  • Power: 125 W MAX
  • Frequency: 47-63 HZ
  • 115 Volts
  • Light Aperture (Model AP-9369)
  • Coupling Bar (Model AP-9369)
Digital Voltmeter (Model 37XR-A)and/or (model FLUKE 111)
  • 2 Connection Cables (Model 8-24)
Stopwatch Function on Alex's Phone(Model LG Envy 2)
Two 9 Volt Batteries
h/e Apparatus (Model AP-9369)
  • 3 Filters
  • Relative Transmission
  • Yellow Line
  • Green Line

Equipment list taken from Alexandra S. Andrego's notebook for this lab User:Alexandra_S._Andrego/Notebook/Physics_307L/2009/09/14

The equipment was already assembled on the day of the lab, but details as to the assembly can be found in Gold's Lab manual linked above.

Procedure and Data

For the first part of this lab I took measurements of the Time for Stabilization, and measurements of the voltages produced for varying strengths of the transmission filter. I also recorded the voltages for each color of light I could see, for some reason Gold lists the ultraviolet part of the spectrum as a viable choice for observation, but I cant see it. For the second part of the lab I recorded the voltages for each color of light, for both orders of spectral lines. The data is shown in the spreadsheet below.

View/Edit Spreadsheet


Here is a plot of the Time for Stablization vs. Transmission Filter.

Here is the plot of Frequency vs Voltage,


The linear fits give V=3.72E-15*f-1.25, and V=3.82E-15*f-1.24, where f is the frequency of the light.

using h=slope*electron charge(from Andrego's notebook) gives

h=5.95E-34, and 6.11E-34 J s

taking the weighted average gives

h=(6.06 +/- 0.38)E-34 J s

using W=e*y intercept(from Andrego's notebook) gives

W=-2.00E-19, and -1.98E-19 J

taking the weighted average gives

W=(-1.98 +/- 0.24) E-19 J

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