User:Manuel Franco Jr./Notebook/Physics Lab 307/2008/10/01

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The Balmer Series For Hydrogen and Deuterium

Lab Partner: David


The objectives are: calibrate an optical spectrometer using the given mercury spectrum in the lab manual, investigate hydrogen and deuterium, compare them, and determine the Rydberg constant for hydrogen.


  • 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.

Images for Experiment


We first had to calibrate the spectrometer by using mercury (Hg) and the table spectral lines of Hg (Lab Manual: Section 4.3).

Hg Spectral Lines

404.7 nm (deep violet very hard to see!!)
435.8 nm violet
skip (very weak blue-green)
546.1 nm green
577.0 nm yellow
579.0 nm yellow
690.75 nm red

The calibration was repeated as need. The colors were aligned using the cross hairs in the eyepiece. We moved the prism as need. Once we calibrated the spectrometer, we adjusted the slit to .7 mm. We adjusted the slit as needed, but we stayed within the bounds of .5 and 1 mm.

As we were calibrating Koch mention the us that the gears in the dial has what is called "slop." So when we calibrated the spectrometer, we calibrated it going counterclockwise. That means all the data measurements have to be taken the same way. If we were to take a data point clockwise, or opposite to direction we initially used to calibrate, our data would be off by about 1 nm. So all the data was gathered going in a counterclockwise direction on the dial.


This is what you should see[1].

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

SJK 02:17, 22 October 2008 (EDT)
02:17, 22 October 2008 (EDT)
I looked at your spreadsheets. They are great! You also have really nice graphs in there. Graphs are an essential part of presenting should upload the images and include them in your report!

This is the Spread Sheet 1 in where I did all my analysis for hydrogen and deuterium.

Color Wavelengths for H Wavelengths for D
Red 656.1 +/- .5 nm 659.13 +/- .03 nm
Blue/Green 486.00 +/- .04 nm 485.95 +/- 0.03 nm
Violet 434.1 +/- .1 nm 434.2 +/- 0.1 nm
Dim. Violet 409.7 +/- .1 nm

409.65 +/- .12 nm

As for the Rydberg constant, I found the constant in this word Spread Sheet 2.

I used this equation to find the slope [2]. And this is the actual measurement thereof [3].

Lab Summary

This is my lab summary.


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