An absorption spectrum is produced when
- A. a hot gas emits light
- B. white light passes through a cooler gas, which removes photons of its own characteristic energies
- C. light passes through a vacuum
- D. a solid is heated until it glows
Explanation
Atoms in the cooler gas absorb exactly the photon energies that match their own energy level differences, leaving dark lines in the continuous background at those wavelengths. The dark lines therefore fall at the same positions as the bright lines the same gas would emit when hot. Fraunhofer lines in sunlight are produced this way by the Sun's own atmosphere.
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