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Balmer Series

see comment
Steven J. Koch 01:30, 13 September 2007 (EDT):Looks like a lot of potentially great data! You two are off to a great start. Description of how to adjust the spectrometer was pretty good. A list of specific equipment you are using would be good, although not sure if your equipment has model numbers etc. Maybe the tubes at least have some labels? And the tube holder/power supply thing probably has a model number.

Adjusting the Spectrometer

This took us a while to figure out how to do. Take a known light seen and wavelength pair. Align the dial to the specified wavelength, now adjust the spectrometer. To adjust the spectrometer you must first remove the prism cover. Loosen the prism's clamp and rotate the prism till the specified color of light falls into the cross hair. Now the measurement that you get for this specific color will be correct. Tighten the clamp and replace the cover.

Materials and set up

Spectrometer (Last years manual has a diagram), a spectrum tube power supply SP200 at 5000 volts, and three various spectrum tubes of Hydrogen Deuterium, and Mercury. We set up the power supply with the correct spectrum tube in front of the spectrometer and turned it on looking through the eyepiece to see the spectrum lines incident from the light. During our initial set up of the experiment we discovered that different results were obtained by approaching the spectral lines from the right then from the left. We decided to fix this problem by taking measurements both from the left and from the right.


Our Measurements

red clockwise- 695 nm, 695 nm, 697 nm, 696 nm, 696.5 nm,

red counterclockwise- 700 nm, 696 nm, 702 nm, 701 nm, 702 nm

yellow 1 clockwise- 576.5 nm, 579 nm, 577.75 nm, 578 nm, 578 nm

yellow 1 counterclockwise- 579.5 nm, 580 nm, 580.5 nm, 581 nm, 580.5 nm

yellow 2 clockwise- 574.5 nm, 574 nm, 576 nm, 576 nm, 575.5 nm

yellow 2 counterclockwise- 576.75 nm, 576 nm, 578 nm, 577.5 nm, 577.25 nm

green clockwise- 544 nm, 544.5 nm, 545 nm, 545.75 nm, 545.25 nm

green counterclockwise- 545.4 nm, 546.1 nm, 547.5 nm, 546.85 nm, 547 nm

violet clockwise- 435 nm, 435.4 nm, 435.25 nm, 435.9 nm, 435.4 nm

violet counterclockwise- 435.75 nm, 435.6 nm, 435.9 nm, 436.2 nm, 436.1 nm


The True Results

red- 690.75 nm

yellow 1- 579 nm

yellow 2- 577 nm

green- 546.1 nm

violet- 435.8 nm

see comment
Steven J. Koch 01:41, 13 September 2007 (EDT):It is terrific that you guys noticed the problem with backlash on the spectrometer screw. Great idea to record it both ways. Multiple measurements will help in estimating your error, as you have done. However, if possible, more than two measurements may make the error estimate easier. We can discuss this next week.

The Hydrogen Light

Our Measurements

red light clockwise rotation- 656.5 nm, 656 nm, 656 nm, 656 nm, 655.5 nm (n=3)

red light counterclockwise rotation- 656 nm, 660 nm, 659 nm, 659.5 nm, 658.5 nm (n=3)

blue light clockwise rotation- 485.5 nm, 485.5 nm, 485.25 nm, 485.5 nm, 485.1 nm (n=4)

blue light counterclockwise rotation- 486.5 nm, 486.2 nm, 486.5 nm, 486.25 nm, 486.75 nm (n=4)

violet light clockwise rotation- 433.5 nm, 434.1 nm, 433.6 nm, 433.6 nm, 433.7 nm (n=5)

violet light counterclockwise rotation- 434.1 nm, 434.1 nm, 434.25 nm, 434.25 nm, 434.3 nm (n=5)

violet #2 light clockwise rotation- 410 nm, 410.5 nm, 410.1 nm, 409.8 nm, 409.6 nm (n=6)

violet #2 light counterclockwise rotation- 410.25 nm, 410.25 nm, 410.25 nm, 410.2 nm, 410.1 nm (n=6)


The True Results

red- 656.3 nm

blue- 486.1 nm

violet- 434.1 nm

violet 2- 410.2 nm

value for R - 10,978,682 m−1 +/- 6000 m−1 the real value for the rydberg constant is 10,973,735.3 m−1 which falls into the std dev. the mean has a .45 percent error from the true value.

The Deuterium Light

Our measurements

red light clockwise rotation- 655.2 nm, 654 nm, 656 nm, 654.5 nm, 655.75 nm

red light counterclockwise rotation- 657.5 nm, 658 nm, 658.5 nm, 659.5 nm, 659 nm

blue-green light clockwise rotation- 484.9 nm, 486 nm, 485 nm, 484.9 nm, 485.1 nm

blue-green light counterclockwise rotation- 486.1 nm, 485.5 nm, 486.1 nm, 486.2 nm, 486.1 nm

violet light clockwise rotation- 434.6 nm, 434.3 nm, 433.6 nm, 433.9 nm, 433.5 nm

violet light counterclockwise rotation- 434.1 nm, 433.95 nm, 434 nm, 434.2 nm, 434.2 nm

violet #2 light clockwise rotation- 409.5 nm, 411 nm, 409.3 nm, 409.6 nm, 409.3 nm

violet #2 light counterclockwise rotation- 410 nm, 409.5 nm, 410 nm, 410.2 nm, 410.1 nm

note violet #2 was really faint and hard to see. The measurements on this color were hard to take and there might be some error in that.


we got 10983540 m-1 +/- 11080.27 m-1 for the rydberg constant for deuterium. this seems right because the rydberg constant for deuterium should not be much different then that of hydrogen.

The Na yellow lines

we could not find the sodium tube.