Spectrum tubes and CD spectroscopes

With no access to the computer laboratory for laboratory ten, I opted to focus on spectra. Summer 2010 I built the laboratory off of a morning lecture on colors, color vision,color blindness achromatopsiacolor constancyretinex and GIMP. This summer the delayed start put laboratory ten on the Tuesday behind midterm and after the DVD Inconvenient Truth was shown to the class on Monday. This meant that I had to cover the midterm and lab hand-back notes along with spectrum material. So I dropped the color material and focused on the electromagnetic spectrum. 

Lavanaleen and Arthur examine the spectrum of hydrogen

In the laboratory session the students worked with CD-ROM based spectroscopes. The class had six to work with. I built one in class so the students could see the construction process. 

After viewing the continuous spectra of the sun, I dug out a box of old spectrum tubes and a spectrum tube power supply also from 1970. Exposed electrodes. 5000 volts. Probably time to buy one the newer units with shielded electrodes or the even newer models without through-the-glass electrodes.


I pushed the 30 second recommended time limit, running hydrogen for up to two minutes at a stretch. This summer I experimented with having the students color the spectrum. Bear in mind laboratory eight did not draw clouds this summer, so the students had not had the often negative experience with crayons and clouds.

Sucyang and Nayleen work on sketching the spectra of the sun, a candle flame, fluorescent lights, and ionized hydrogen plasma.


Some students felt that they could not color, so a coloring expert was brought in and on hand to assist the students who needed help selecting and using crayons. If nothing else, her presence, coloring skill, and age, left the college students with little to complain about. Can you color as well as a second grader? 

Mary-ellen works on her spectra

Sucyang studies notes on the board while Nayleen continues her sketching

The interaction between the CD surface, the digital camera wavelength sensitivity, and color balance choices  being made by the digital camera yield images that do not accurately capture the colors perceived by the human eye. The rightmost band of this image of the hydrogen tube was distinctly purple.

The HyperPhysics site has an excellent diagram of the electron transitions that generate the above three spectral lines.


This image is also of hydrogen, but the way the disk diffracted the colors the high frequency purple band is on the left. The spectral bands are in the Balmer visible series. The red band is 656 nanometers, the cyan band is likely 486 nanometers, and the blue-purple band is probably 434 nanometers.


The tubes are unmarked - the labels fell off decades ago. A gas with a strong yellow spectral band - sodium perhaps?

The laboratory lasted just over two hours.

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