Resolving Spectral Lines with a Periscope-Type DVD Spectroscope

A new type of DVD spectroscope, the periscope type, is described and the numerical analysis of the observed emission and absorption spectra is demonstrated. A small and thin mirror is put inside and an eighth part of a DVD is used as a grating. Using this improved DVD spectroscope, one can observe and photograph visible spectra more easily and clearly than with an earlier design. The spectra photographed using a digital camera were digitized using a software that is available from a free public source and were numerically analyzed using a conventional spreadsheet. Spectral charts of the emission spectra of a fluorescent lamp, discharge lamps of hydrogen and helium, sunlight, Na flame test, and the absorption spectrum of KMnO4 aqueous solution are reported. Small features are discernible in the spectra. For the sun spectrum, many Fraunhofer lines were clearly observed and some of the lines are assigned to Na, H, Fe, Mg, and Ca elements. For the Na flame test, the D line was clearly resolved to two distinct peaks at 589.0 and 589.6 nm when a pair of razor blades was used as a slit. Those results show that this periscope-type DVD spectroscope has the potential to be a cost-effective, powerful, and versatile tool for science education.