Physics307L:People/Smith/Notebook

Lab Summaries

Lab 1: Oscilloscope Lab

• See lab manual for what this lab was about.
• See my Lab Notebook entry for my remarks and recorded data.

Data

Reported value for fall time using AC coupling:

• The Digital Storage Oscilloscope (DSO) has a built in function to measure "fall-time". It reported 239.6ms to 241.0ms. This was believed to be incorrect.
• Using the cursors in the DSO interface to measure the time between the peak value and 10% of that value and using a frequency of between 2.343Hz and 2.430Hz reports a value of 58.00 ms.
  • Subsequent measurements using this method after changing the frequency on the frequency generator:
    • Frequency: 4.798Hz - 5.061Hz, fall time: 57.00ms.
    • Frequency: 7.257Hz - 7.262Hz, fall time: 55.00ms.

Note: The DSO displays these times in integer values of milliseconds. Therefore, the precision of these measurements is necessarily limited. I suspect the way the DSO rounds these numbers makes the screen display, for instance, 55.00ms for any measurement between 54.5ms and 55.5ms.

What did you learn?

I had little previous experience with oscilloscopes before this lab. I was able to familiarize myself with the the way oscilloscopes are hooked up, how they used to work (scanning CRT displays, etc), and to interact with the modern DSO we used (it has an interface similar to an ATM machine, with many useful functions able to be selected and displayed using the buttons on its face.) I also learned a bit about the concept of AC coupling, which I had never heard of before. I also wrote my first lab notebook entry in the wiki format, which was very straightforward.

What could make the lab better next year?

Well, I saw a video online of someone who interfaced an oscilloscope with a soundcard on his PC and was able to do very, very impressive things; he wrote things on the screen, had very neat patterns and effects. I don't think we should do all that, but it's an interesting concept, and it might be worth explaining how someone would be able to do all that. You can see the video here.

Lab 2: Balmer Series

• See my Lab Notebook entry for procedure, remarks and recorded data and analysis.

Purpose

The objective of this lab is to experimentally determine the value of the Rydberg Constant by measuring the atomic emission spectral wavelengths of hydrogen and the hydrogen-like element deuterium (which is hydrogen with an extra neutron thrown in).

Data

Many measurements were taken and recorded. They are able to be seen in the data collected section of my lab notebook entry.

I used Excel to analyze the data (you can see my Excel spreadsheet here). I used our measurements of the wavelengths of the atomic emission spectra of hydrogen and of deuterium to calculate the measured Rydberg Constant (they are, believe it or not, slightly different despite the name "Rydberg Constant"). I also calculate the expected Rydberg Constant for hydrogen and deuterium by using fundamental physical constants, and compared these with our measured values. They are reported below:

		Expected Rydberg Constants	Measured Rydberg Constants	Percent Difference
Hydrogen	Clockwise	1.09677286888108E+07 [math]\displaystyle{ m^{-1} }[/math]	1.09797802016246E+07 [math]\displaystyle{ m^{-1} }[/math]	-0.1099%
	Counterclockwise	1.09677286888108E+07 [math]\displaystyle{ m^{-1} }[/math]	1.09583397614656E+07 [math]\displaystyle{ m^{-1} }[/math]	0.0856%
Deuterium	Clockwise	1.09647449477397E+07 [math]\displaystyle{ m^{-1} }[/math]	1.09846377155094E+07 [math]\displaystyle{ m^{-1} }[/math]	-0.1814%
	Counterclockwise	1.09647449477397E+07 [math]\displaystyle{ m^{-1} }[/math]	1.09636035647508E+07 [math]\displaystyle{ m^{-1} }[/math]	0.0104%

And our best estimates of our measured Rydberg Constants:

		Measured Rydberg Constants (in m-1)
Hydrogen	Clockwise	10979780.2016246 [math]\displaystyle{ \pm }[/math] 2810.24625
	Counterclockwise	10958339.7614656 [math]\displaystyle{ \pm }[/math] 3908.3275
Deuterium	Clockwise	10984637.7155094 [math]\displaystyle{ \pm }[/math] 6215.96625
	Counterclockwise	10963603.5647508 [math]\displaystyle{ \pm }[/math] 3312.62625

Links to Lab Entries

Wednesday Labs
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