Spectroscope Lab, from "College Astronomy Kit" PS-13

What you turn in to your instructor as a lab

Assemble the spectorscope in your "Learning Technologie's" "College Astronomy Kit" per the instructions in Activity 2 "BUILDING A SPECTROSCOPE." After you have it assembled there is one trick in getting it to work. The disk at the end, the diffraction grating disk, that reflects rainbows, need to be truned within the slite until the spectrum, the colors fall between the numbers.

Notice that nano meters which measure wavelength and eV, electron Volts, which measure energy have opposite numerical trends one increase while the other decreases. This is just an expresion of Plank's Law E=h* c/lamda where E is the energy of a photon, lambda is the wavelength, h is Plank's constant, and c is the speed of light. Plank's law is also commonly stated as E=h f where f is frequency. These equaiton are the same since c= lambda f and solving for f, the frequency one gets f=c/lambda.

Please turn in at least three spectral observation using the "Spectroscope observation Report form."

One must be of an incandeasent light that shines because it is hot like a tungstein filiment light. The spectrum of an incandasent light will have all of the colors in the rainbow with no gaps.

The second spectral observation must be of the sun. Just point the spectroscope to a bright piece of the sky; the slite that lets the light in does not have to be directly pointed at the sun, in fact, if I were you I would not want to risk my eye sight by pointing it directly at the sun. You should see something that looks like an incandasent light with all the colors of the rainbow, but when you look at it carefully perhaps after changeing the contrast a bit by moving the slite around a bit you will see that the rainbow has a few bearly discernable dark, absorption lines. These aborption lines first seen by Franhoffer in the 19 century are the absorption lines caused by the atmosphere of the sun. There pattern tells astrophysical spectroscopers that the sun is spectral type G2.

The third spectral observation must be a florescent light.

You are encourage to do more spectral observation reports like a discharge lamp in a shopping mall or a drinking establishment. With a discharge lamp the glowing ionized plasma is generally in a thin tube and you will need to place the slight that lets in the light on the big end with the pointer next to the discharge lamp. Orange discharge lamps are often filed with neon gas and will show you a pretty neon emission spectra. Blue and Red discharge lamps are other gases or gas mixtures and will show an emission spectra, too, but it will be differnt than neon. You may want to have fun while becoming a spectral explorer, show the spectra to other people around you they will appreciate the beauty of the natural world and the vivid clear color seperation. Security guards at malls may particularly want to look at what you are doing and they may recruit their buddies to look in the device if you are smart enough to share the look with them and a bit of an explaination.

There are actually two major types of florescent light around with markedly differnt spectra. The ones with only a few lines in red, green, and blue are much more energy efficeint than the old style floresent bulbs which show a bright line in the blue and green sorrounded by a quasi-continium. Floresent bulbs are actually mercury discharge lamps that produce a few emission line in the visible and much ultraviolet radiation inside the tube. The white stuff inside the tube which is slightly posinous if you get it in a cut or breath it in absorbs the ultraviolet, high energy photons, and floreses many lower energy photons in the visible. The differnt white phosphores used in different tubes produce differnt spectra. The old style lights and spectra flash with a 60 cycle duty that irrate very sensative people while consuming more energy than the newer ones with only a few colors in the spectra that flash with around 60,000 cylces, that probably do not irrate sensative people, not even dogs can hear at this frequency.