Iron Sparks
After pushing a button to bring the exhibit to life, the visitor turns a knob which feeds an iron rod into a slowly turning wire brush. The brush and rod are connected to opposite ends of a high current power supply. When the rod touches the brush, blue-white sparks fly. If the light from the sparks is examined with a spectroscope hanging from the exhibit, it will be noted that the blue-white light is a combination of the thousands of discrete spectral lines made by a complicated atom like iron. By comparison, the spectrum of a simple element, like helium gas, produces a relatively simple spectrum. The visitor can view the spectrum of helium through the same spectroscope or with a diffraction grating.
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