What Is the World Made Of?


In what ways do atoms emit and absorb light?

In the mid-1800s Robert Kirchhoff published three laws that describe how materials emit and absorb light:

  1. A hot solid or a hot, dense gas produces a continuous spectrum.
  2. A hot, low-density gas produces an emission-line spectrum.
  3. A continuous spectrum source viewed through a cool, low-density gas produces an absorption-line spectrum.


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