ASTRO-110 Lecture Notes - Lecture 26: Black-Body Radiation, Energy Flux, Absorption Spectroscopy
18 Sep 2020
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Document Summary
When a hot solid, liquid or very dense gas is viewed through a spectroscope a continuous spectrum such as that shown above is seen. The spectrum is a continuous smear of coloured light from blue-violet to red with no apparent structure. In fact there is an overall structure which can be seen if the intensity at every wavelength is measured (including the non-visible portions) and plotted as a graph against the wavelength. Such graphs are called "blackbody radiation curves" and are shown in the text as fig. These curves are very important and contain a great deal of information. I would like you to notice 3 important points. The intensity increases at every wavelength as the temperature increases; the curves never cross each other. The total radiated energy (or energy flux, f), which is the area under the curve, increases very rapidly with the temperature. In fact it increases with the 4th power of the absolute temperature.
