User:Johnny Joe Gonzalez/Notebook/Physics 307L/2009/09/30

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Balmer

SJK 12:06, 21 October 2009 (EDT)
12:06, 21 October 2009 (EDT)Good job with safety, materials, the photos, and the embedded spreadsheets.  The number one deficiency with your primary notebook (this page) is still that you need to write much more about what you're doing (in words).  As is, there are important things missing that would prevent reproducing the experiment (see more comments below).
12:06, 21 October 2009 (EDT)
Good job with safety, materials, the photos, and the embedded spreadsheets. The number one deficiency with your primary notebook (this page) is still that you need to write much more about what you're doing (in words). As is, there are important things missing that would prevent reproducing the experiment (see more comments below).

Safety

  • Check for exposed wires or loose connections as voltages as high as 5kV can be used.
  • There are glass components, be careful when handling the glass tubes.
  • One of the glass tubes is filled with mercury, as mercury is toxic to humans take care when handling it.
  • careful not to break or damage the prism

Materials

A picture of the Spectrometer and lamp
A picture of the Spectrometer and lamp
  • Dr. Gold's Lab manualGold's Physics 307L Manual
  • Constant-Deviation Spectrometer ser.(12610)
  • Spectrum tube power supply(model )
  • 5 sheets of paper (for measuring slit width)
  • mercury tube
  • flashlight

Procedure

  • First we aligned the prism so that the light from the lamp is reflected to the eyepiece. This part can take sometime, though once it's aligned then calibrating the spectrometer is simple.


Calibrating

First thing we did is calibrated the spectrometer. We did this by locating a line of the mercury spectrum and compared where we found the lines as opposed to the data given, we then adjusted the line until it matched the data, after which we double checked our results by searching for other lines on the mercury spectrum and then compared it to our results.SJK 11:46, 21 October 2009 (EDT)
11:46, 21 October 2009 (EDT)From your notes here, it's not clear whether you recalibrated for day 2.  Or did you just re-check your numbers?
11:46, 21 October 2009 (EDT)
From your notes here, it's not clear whether you recalibrated for day 2. Or did you just re-check your numbers?
View/Edit Spreadsheet
View/Edit Spreadsheet

Procedure Continued

  • Once calibrated, we replaced the mercury lamp with a hydrogen lamp.
  • Following the same procedures as when calibrating, we looked for the four lines of the hydrogen spectrum and then recorded the measured wavelengths. The wavelength's measurements are shown below
  • The first data chart is for day 1 only one trial was made since we were still getting familiar with the equipment. Day 2 data is seen below for both hydrogen and Dueterium.
SJK 11:51, 21 October 2009 (EDT)
11:51, 21 October 2009 (EDT)It seems to me that there's some important information missing:  Did you account for gear backlash?  Did you turn clockwise or counterclockwise?  Were you sure to turn the same way as when you were calibrating?  I'm sure you knew all of this information, but it doesn't appear to have been written down, and eventually you will forget it, making it impossible to reproduce these results in the future.  There's a lot of other important information probably missing as well.  E.g., I notice above you have sheets of paper for measuring the slit width (great idea!)  but no description of what you did with that (as far as I see so far).  In the future, work hard to record a lot of information in this (your primary notebook)--it takes time but is very important!
11:51, 21 October 2009 (EDT)
It seems to me that there's some important information missing: Did you account for gear backlash? Did you turn clockwise or counterclockwise? Were you sure to turn the same way as when you were calibrating? I'm sure you knew all of this information, but it doesn't appear to have been written down, and eventually you will forget it, making it impossible to reproduce these results in the future. There's a lot of other important information probably missing as well. E.g., I notice above you have sheets of paper for measuring the slit width (great idea!) but no description of what you did with that (as far as I see so far). In the future, work hard to record a lot of information in this (your primary notebook)--it takes time but is very important!

data

View/Edit Spreadsheet


View/Edit Spreadsheet

Data Analysis

Next we found the Rydberg Constant by taking the measured wavelengths and applying it to the equation:
\frac{1}{\lambda }=R(\frac{1}{2^{2}}-\frac{1}{n^{2}}), where, n=3,4,5....
and isolating R
R=\frac{1}{\lambda }\frac{1}{(\frac{1}{2^{2}}-\frac{1}{n^{2}})}

SJK 12:04, 21 October 2009 (EDT)
12:04, 21 October 2009 (EDT)You should continue on your sheet and calculate the SEM from the standard deviation, and then you will be able to report wavelengths +/- uncertainty.  THEN, when you compute R, you can propagate the uncertainty from the wavelength to be uncertainty in R.
12:04, 21 October 2009 (EDT)
You should continue on your sheet and calculate the SEM from the standard deviation, and then you will be able to report wavelengths +/- uncertainty. THEN, when you compute R, you can propagate the uncertainty from the wavelength to be uncertainty in R.

Unfortunately the day 2 data only has one measurement for hydrogen, so our error will be considerable, when compared to our data for dueterium.

View/Edit Spreadsheet
View/Edit Spreadsheet


Plugging in the variables we get the following solutions for: R=\frac{1}{\lambda}\frac{1}{(\frac{1}{2^{2}-n^{2}})}

View/Edit Spreadsheet

I know that the number for the first violet line is off, I think that we had accidently recorded the second violet line instead of the first on our second measurement, thus the huge shift in error there, but I still felt it was important to write down all of the data found.SJK 11:55, 21 October 2009 (EDT)
11:55, 21 October 2009 (EDT)Yes, I agree it's very important to record the data before you decide to throw it out.  That's great experimental technique on your part!  We haven't formally discussed "throwing out data" yet, but in a case like this, it is very appropriate to disregard the measurement, as the likelihood of that being a random error is miniscule.  But it's also important to record in your notebook, just in case it wasn't a mistake, but some other rare phenomenon or otherwise important event that would help a future researcher out.
11:55, 21 October 2009 (EDT)
Yes, I agree it's very important to record the data before you decide to throw it out. That's great experimental technique on your part! We haven't formally discussed "throwing out data" yet, but in a case like this, it is very appropriate to disregard the measurement, as the likelihood of that being a random error is miniscule. But it's also important to record in your notebook, just in case it wasn't a mistake, but some other rare phenomenon or otherwise important event that would help a future researcher out.

The next set of R values are for the dueterium.

View/Edit Spreadsheet
SJK 11:59, 21 October 2009 (EDT)
11:59, 21 October 2009 (EDT)I see now that you put more analysis on your "summary" page.  It would be better to continue it here, and to put the final answers and comments on the summary page.
11:59, 21 October 2009 (EDT)
I see now that you put more analysis on your "summary" page. It would be better to continue it here, and to put the final answers and comments on the summary page.


Other Links and Acknowledgements

I used to obtain the n values for the line spectrum
wiki page I used to confirm the n values and further help my understanding of the Balmer series
My lab summaryMy Balmer Series Lab Summary



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