Physics307L F08:People/sosa/Lightspeed

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Image:Balmer3.gif Balmer Series Lab Notebook


Lab Partner: F08:People/Franco Manuel Franco

We are going to learn how to calibrate the spectrometer using the known mercury spectrum. Then we are going to try to measure the hydrogen Balmer lines to determine the Rydberg constant. We'll measure the deuterium spectrum and we will try to determine how the Rydberg constant varies between hydrogen and deuterium.


  • Adam Hilger London Spectrometer. A Serial Number 12610 was found.
  • Power Supply, 5000V 10mA,(Model: Sp200 from Electro Technic products)
  • A Prism
  • A Hydrogen Tube from Cenco Scientific Company.
  • A Deuterium Tube from Cenco Scientific Company.
  • A Mercury Tube from Cenco Scientific Company.

Some images of the materials used


At the beginning of the lab Manuel and I attempted to use the mercury lamp to calibrate the spectrometer. Since we could not identify

the mercury lamp we started to check other lamps to calibrate the spectrometer. We decided to used one of the other lamps available

to calibrate the spectrometer. We thought that the neon lamp would be a good choice. As it turns out it was not. Our measurments of

the hydrogen spectrum were pretty bad. We tried again with helium. And we got very bad measurments as well. Finally playing around

with the lamps we were able to identify the mercury lamp, thanks to its very characteristic two yellow lines. (seen below).


  • Mercury spectrum: Notice the pair of yellow lines at 576.959 nm and 579.065 nm

With the mercury lamp identified, we proceded to calibrate the spectrometer and measure the spectral lines of the hydrogen and the



1st lab Hydrogen Measurements

Color Measurement 1 (nm) Violet at 435.8 nm.
Red 660.5
Blue/Green 486.0
Violet 434.1
Dim. Violet 410.4
Attention: This data should be disregarded since we did not take into account the gear back lash.

Hydrogen Measurements

Color Measurement 1 (nm) Measurement 2 (nm) Measurement 3 (nm) Measurement 4 (nm)
Red 657.8 659.9 659.5 659
Blue/Green 486 486 486.1 485.9
Violet 433.8 434 434.2 434.4
Dim. Violet 409.7 409.8 409.3 410.1

Deuterium Measurements

Color Measurement 1 (nm) Measurement 2 (nm) Measurement 3 (nm) Measurement 4 (nm)
Red 659 659.9 659.5 658.1
Blue/Green 485.9 485.9 486 486
Violet 434.2 434.2 434.2 434.2
Dim. Violet 409.8 409.7 409.8 409.3

Data Analysis

Balmer Series Spread Sheet

Color Wavelengths for H Wavelengths for D
Red 659.05 +/- 0.45 nm 659.13 +/- .03 nm
Blue/Green 486.00 +/- 0.04 nm 485.95 +/- 0.03 nm
Violet 434.1+/- 0.13 nm 434.2 +/- 0.0 nm
Dim. Violet 409.7 +/- 0.16 nm

409.65 +/- .12 nm

Calculated Rydberg constant for hydrogen = 1.0966E+07(+/- .0003) (1/m) 0.062% difference with the original value
Calculated Rydberg constant for deuterium = 1.0969E+07(+/- .0003) (1/m) 0.041% difference with the original value


Our calculated results for the Rydberg constant seem agree pretty well with the accepted values. This is a bit surprising to me since

our result for the red line in both hydrogen and deuterium was way off. This lab was very useful for me because it helped me to

reinforce the concepts of standard deviation and standard error.


  1. Lab Manual: Sections 4.1-4.6
  2. Wikipedia article on Balmer Series
  3. Wikipedia article on Rydberg Constant

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