User:Brian P. Josey/Notebook/Junior Lab/2010/11/22: Difference between revisions
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==Equipment== | ==Equipment== | ||
[[Image:2010-11-22 14.06.12.jpg|thumb|right|Spectrometer]] | |||
[[Image:2010-11-22 14.06.16.jpg|thumb|right|Vapor Tube Power Supply]] | |||
[[Image:2010-11-22 14.11.58.jpg|thumb|right|Internal Prism]] | |||
* Constant deviation spectrometer | * Constant deviation spectrometer | ||
* Spectrum Tube Power Supply Model SP200, 5000 volts, 10MA. | * Spectrum Tube Power Supply Model SP200, 5000 volts, 10MA. | ||
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** hydrogen | ** hydrogen | ||
** deuterium | ** deuterium | ||
To set-up the experiment, we put a vapor tube into the power supply, and turned it on. We then aligned the constant deviation spectrometer up with tube. The spectrometer had to be calibrated first, however, to account for any discrepancies in the measurements. This is explained in the methods section below. | |||
==Methods== | |||
[[Image:2010-11-22 14.37.21.jpg|thumb|right|Mercury]] | |||
[[Image:2010-11-22 14.52.35.jpg|thumb|right|Hydrogen]] | |||
[[Image:2010-11-22 15.06.07.jpg|thumb|right|Deuterium]] | |||
After setting up the experiment, we proceeded to calibrate the constant deviation spectrometer. The first step in the process was to find a spectral line through the eyepiece, and focus the cross hairs on the center of the line so that both the line and the cross hairs were in focus. This is accomplished by turning the knob on the center of the arm with the eye piece. The second step was to calibrate it so that our measurements came very close with the accepted values of some known wavelengths, in this case mercury vapor. To adjust the prism, we turned the large knob marked with wavelengths to the accepted value, and then adjusted the prism itself with the knob on it so that the spectral line was focused on the cross hairs. Fortunately, being the last group in the class, the spectrometer was already very closely calibrated, as our measurement, in the table below illustrate. | |||
We then moved on to measure the values of wavelengths of light coming from the hydrogen and deuterium vapor tubes. This was accomplished by turning the marked knob carefully while watching the lines move through the eyepiece. When the prominent lines were centered on the cross hairs of the eyepiece, we then recorded the wavelength from the marked knob. For all three vapor tubes, there was more than just the principle spectral lines, and there was even some continuity in the spectrum. The extra spectral lines could be the result of small amounts of gasses from other compounds being in the tube, while the continuous spectra is from impurities in the glass prism, which is fairly old and had to stand up to years of use. Also, because the gears that rotate the prism are not perfectly aligned in one direction, if we overshot a spectral line, we would rotate back a quarter turn and then more in more carefully on the line. This would eliminate error for the gears in our measurements. | |||
This table summarizes both our data, and the conclusions that we inferred from the data: | |||
<center> | |||
{{ShowGoogleExcel|id=0AjJAt7upwcA4dHdIYVZoMjA4al9GbmV3b3J5QjJ3RGc|width=750|height=325}} | |||
</center> | |||
==Analysis and Results== | |||
<math> | |||
\frac {1} {\lambda} = \frac {1} {R} (\frac {1} {n^2} - \frac {1} {m^2}) | |||
</math> | |||
where: | |||
* '''λ''' - is the wavelength of the released photon, | |||
* '''R''' - is the Rydberg constant, | |||
* '''n''' - is the principle quantum number of the lower energy state that the photon drops to, and | |||
* '''m''' - is the | |||
This week, I'm going to do the Balmer series lab to measure the wavelengths of both hydrogen and deuterium gases. | |||
To do this, we first have to measure the known wavelengths of Mercury to calibrate the telescope and then measure the wavelengths of the hydrogen and deuterium. | |||
Revision as of 12:13, 5 December 2010
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Balmer SeriesThis week, we attempted to measure the Rydberg constant in the Balmer series lab. The Rydberg constant is a constant that is used in a formula for predicting the wavelength of a photon that is released when an excited electron drops to a lower level, or the wavelength needed to raise an electron from a lower to a more excited state. To do this, we measured the well known Balmer series, which occurs when the electrons drop from a higher excited state to the second orbital (n=2 orbital). To do this, we first calibrated our instruments with a Mercury tube, and known values for wavelength, and then measured the wavelengths of light for both hydrogen and deuterium. Equipment  
To set-up the experiment, we put a vapor tube into the power supply, and turned it on. We then aligned the constant deviation spectrometer up with tube. The spectrometer had to be calibrated first, however, to account for any discrepancies in the measurements. This is explained in the methods section below. Methods   After setting up the experiment, we proceeded to calibrate the constant deviation spectrometer. The first step in the process was to find a spectral line through the eyepiece, and focus the cross hairs on the center of the line so that both the line and the cross hairs were in focus. This is accomplished by turning the knob on the center of the arm with the eye piece. The second step was to calibrate it so that our measurements came very close with the accepted values of some known wavelengths, in this case mercury vapor. To adjust the prism, we turned the large knob marked with wavelengths to the accepted value, and then adjusted the prism itself with the knob on it so that the spectral line was focused on the cross hairs. Fortunately, being the last group in the class, the spectrometer was already very closely calibrated, as our measurement, in the table below illustrate. We then moved on to measure the values of wavelengths of light coming from the hydrogen and deuterium vapor tubes. This was accomplished by turning the marked knob carefully while watching the lines move through the eyepiece. When the prominent lines were centered on the cross hairs of the eyepiece, we then recorded the wavelength from the marked knob. For all three vapor tubes, there was more than just the principle spectral lines, and there was even some continuity in the spectrum. The extra spectral lines could be the result of small amounts of gasses from other compounds being in the tube, while the continuous spectra is from impurities in the glass prism, which is fairly old and had to stand up to years of use. Also, because the gears that rotate the prism are not perfectly aligned in one direction, if we overshot a spectral line, we would rotate back a quarter turn and then more in more carefully on the line. This would eliminate error for the gears in our measurements. This table summarizes both our data, and the conclusions that we inferred from the data: {{#widget:Google Spreadsheet |
key=0AjJAt7upwcA4dHdIYVZoMjA4al9GbmV3b3J5QjJ3RGc | width=750 | height=325
}} Analysis and Results[math]\displaystyle{ \frac {1} {\lambda} = \frac {1} {R} (\frac {1} {n^2} - \frac {1} {m^2}) }[/math] where:
To do this, we first have to measure the known wavelengths of Mercury to calibrate the telescope and then measure the wavelengths of the hydrogen and deuterium.
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