Demos: 7B-15 Line Spectrum

Different discharge tubes are viewed successively through a diffraction grating. The emission line spectra are clearly seen. Available spectral tubes are: Argon, Carbon Dioxide, Deuterium, Helium, Hydrogen, Krypton, Mercury, Neon, Nitrogen, Oxygen, Water and Xenon.

Directions: Place the spectral tube on the rotating turntable so that the tube is facing the class and at the back side of the table. On the opposite side place the large diffraction grating. With the room lights dim, slowly rotate the turntable so that different segments of the class can observe the spectra.

Suggestions for Presentation: It often is difficult for students to accept that the spectrum they see is really different “pictures” of the glowing tube. Discuss how the color they see in the tube (without passing through the grating) is a composite of colors unique to that particular gas. The colors are separated by the grating.

Applications: Identification of elements in stars

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