emission line



  • Bright line seen in an emission spectrum. Usually caused by radiation from a hot gas superimposing its spectrum on the radiation from a cooler object, as with the Sun’s outer atmosphere modifying radiation from the Sun’s surface. If emission processes in the gas are using all the energy passing through it, a spectrum can consist entirely of bright lines on a dark background. Otherwise the observer sees bright lines on a background which also contains radiation, but at a lower level of energy.