Physics307L F07:People/Le/balmer

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SJK 01:45, 19 November 2007 (CST)
01:45, 19 November 2007 (CST)
Link to your primary lab notebook notes?


The purpose behind this lab is to discover the Rhydberg Constant of light emission spectra. When gasses are excited, they emit light at certain freqencies. We can look at the spectra and then determine what gases we are dealing with.

In order to do this, we used a "constant deviation" Spectrometer and looked at the emission spectra of hydrogen and deuterium. The spectrometer allowed us to calculate the wavelength of the light bands we were seing, and comparing them with the excitation level, we are able to calculate the constant.

| Link to my Lab Notebook


After measuring the wavelenghts of light bands, and plugging it into the formula above , I was able to tabulate this table of the Rhydberd Constatnt for each data set.

MATLAB doesnt include units on it's numbers, so all of these are measured in inverse meters


The data was very good, and the lab itself was not full of errors.

Taking each of the values above, and comparing it to the accpeted value of the Rhydberg Constant, we can get a rough %error

percent_err =

    redhyd: [0.5313 0.2244 0.2244 0.8402]
   bluehyd: [0.3247 0.2626 0.0769 0.4906]
    viohyd: [0.1553 0.1784 0.0860 0.2709]
   viofhyd: [0.1693 0.1204 0.1204 0.0716]
    reddet: [0.7473 0.2244 0.2550 0.8402]
   bluedet: [0.4076 0.2007 0.3040 0.4283]
    viodet: [0.3172 0.2360 0.0629 0.6242]
   viofdet: [0.0960 0.5831 0.1938 0.5108]
    of_avg: 0.1960

Final Thoughts

SJK 01:53, 19 November 2007 (CST)
01:53, 19 November 2007 (CST)
From your summary and lab notebook, it wasn't clear that you appreciated the physics of what you were investigating (versus just plugging and chugging on numbers). Where does Balmer series arise from? What about discussion of difference between hydrogen and deuterium? etc. Otherwise, it is good data analysis.

This was a pretty good lab, despite the antiquated equipment. The big thing that would need to be changed was the dial used to measure the wavelength. The partitions on it were not very good and it itself was clunky. If that could be updated, the data and the lab (albeit the lab came out fine) would be much more accurate.

Other possible sources of error could be the alignment of the prism and any ambient light that may seep in past the source.

Also, when observing the light, the width of the band got bigger as you let in more light. You had to measure it from the right most section. Closing the slit that let light in helped alieviate this problem, but it gets harder and harder to see.

As for my final estimate of the Rhydberg Constant, it should lie within 1 standard deviation of the data.

SJK 01:44, 19 November 2007 (CST)
01:44, 19 November 2007 (CST)
You should technically put parentheses around the two values, so that units are on both, but it's obvious what you mean. Also too many digits on the uncertainty...only the first or maybe first two are significant. Finally, did you use the standard deviation or standard deviation / sqrt(N)?