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Exploring Kirchoff's Laws

SPU-21 Fall 2014

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Kirchoff's laws state that when a cool gas lies in front of an opaque hotter object, the cool gas will absorb more light from the hot object than it emits by itself, so an absorption line spectrum results. The lines appear at wavelengths where atoms in the overlying cool gas can absorb light of that energy to undergo an electron transition to a higher energy level (as discussed in class). The relatively cool solar "atmosphere", overlaying the hotter surface layers (photosphere) of the Sun, is a perfect example. But if the gas is hotter than the background source, the gas emits more light at its favored atomic transition (or lin) wavelengths than it absorbs, so an emission line (i.e. a line that has greater intensity than the neighboring "continuum") results.

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