edited by GEORGE L. GILBERT Denison University
Granville. Ohio 43023
Spectroscopy in Large Lecture Halls SUBMITTEDBY
Fred Juergens Unlverrlty of Wisconsin Madl~on.WI 53706 CHECKD BY
George L. Gilbert oeniron Unlverlsly Granville. OH 43023
The availability of inexpensive transmission diffraction gratings' makes i t possible to display spectral phenomena to groups of students. Hughes has described how to make individual spectroscopes using such gratings, plastic tubing, and slits made with pairs of razor blades2. Although these spectroscopes could he passed around to a small class, they are impractical for a large group. We demonstrate both continuous and discontinuous spectra to 350 students in a large lecture hall by using large sheets of the grating material with various light sources. Materials One 15-W fluorescenttube mounted vertically, with necessary sockets, power supply, and line cord. Alternatively, two 6-W fluorescent tubes mounted end-bend may be used. One 25-W aquariumlight bulb, socket, switch, and line cord. Sucha bulb must have a straight filament to be useful. Two gas discharge tubes about 40 cm long, one filled with neon and another filled with argon gas plus a little mercury. (See construction section for details.) Neon sign transformer with wire leads to connect to the two ends of a discharge tube. Diffraction grating, about 200 cm by 77 cm, mounted in a cuwed frame. (See constuction section for details.) Low-power helium neon laser (optional). White cardboard about 50 cm square, mounted in a vertical position, to serve as a pnqw tim ween lor laser bpam (opt~onal~. Smnll prece of transmission grating material nhuur 5 rmsquare to be monnted in fnmt of h e r apcrrure
