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THE LAWS OF SPECTROSCOPY
Gustav Kirchoff articulated some basic phenomena that occur when light flows through matter. These rules are fundamental tools when performing spectroscopy, which is the study of matter from the light that comes from or through objects. The laws are straightforward. - Light flowing through high-density, low-energy gas produces absorption lines. The patterns of the lines reveal the elements or compounds in the gas. - Light flowing from low-density, high-energy gas produces emission lines. The patterns of the lines reveal the elements or compounds in the gas. - Light flowing from high-density, high-energy gas produces continuum light. The shape of the continuum reveals the process that energizes the gas. If, for example, the gas has been energized by being heated to a temperature higher than its surroundings, then the continuum light will be thermal radiation. Any, all or none of these features can appear in a spectrum. The combination of the spectral information from light sources reveal a great deal about those sources, and is often the only tool that can be used to learn about much of our universe. Spectroscopy is particularly important in astronomy - a science that depends critically on the light coming from distant objects. |