User:Alex G. Benedict/Notebook/Physics 307L: Junior Lab/Balmer Series Lab

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Steve Koch 04:18, 21 December 2010 (EST):Good primary lab notebook, but a little more detail necessary to ensure reproducibility.

Balmer Series Lab

This lab was performed in the junior laboratory in the UNM physics building on October 25 and November 1, with Joseph Frye.


[Dr. Gold's Lab Manual]

Joseph Frye's Notebook

Equipment and Setup

Thanks to David K. O'Hara for the specific model numbers of the equipment used. O'Hara's Lab from 2009

  • Adam Hilger London Spectrometer. Serial Number 12610
  • Spectrum Tube Power Supply Model SP200 5000V 10 mAmps
  • Spectrum Tube, Mercury Vapor S-68755-30-K
  • Spectrum Tube, Hydrogen S-68755-30-G
  • Spectrum Tube, Deuteruim S-68755-30-E

Set up for this lab involved putting a tube in the power supply and aiming the spectrometer towards the tube. Also putting some books under the power supply to elevate it.

Procedure and Data

We followed the procedure in the lab manual linked above. On the first day we followed the calibration procedure on this page: [Balmer]. On the second day, we first observed the spectral lines from the Hg source for a few trials moving forwards and then backwards. We did this to account for the slight shift in the measured position of the spectrometer due to improper gear meshing. Then created least squares fits for the forwards and backwards trials. Which were then used to correct measurements taken that day. We then observed the locations of the spectral lines of the H and D.

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We know from the Rydberg formula that R=1/((wavelength of the light)*(1/4-1/n^2)), the accepted value is 0.0109737316 nm^-1 for hydrogen. And using the definition of the Rydberg constant, it should be 0.01097072 for Deuterium.

For the first day:

We get for hydrogen:


Which gives a relative error of 0.00085 and a fractional error of 0.0024

and for Deuterium:

R=0.01098897 +/-0.000021

Which gives a fractional error of 0.0019 and a relative error of 0.00055

For the second day:

For H:

R=0.01099695+/- 0.000026

Which gives a relative error of 0.0021 and a fractional error of 0.00241

For D:


Which gives a fractional error of 0.002 and a relative error of 0.001

Overall there was very good data, and the experiment went very well.