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Now, let us make a spectrum of the Sun.  Here is what we see: A spectrum like that from a light bulb. But, in addition, Superimposed are dark lines - called Fraunhoffer lines   after their discoverer.   Blackbody Radiation Every object emits and reflects radiation.  Consider an object that reflects NO  radiation.  It therefore only emits radiation and is what we call a perfect radiator.  But if reflects nothing, then when light shines on it, all that light is absorbed, then  it is also a perfect absorber.   Definition : An object that is a perfect emitter and absorber is called a blackbody. From Experiment:  Blackbodies emit radiation at all wavelengths, but not in  equal measure.   Radiation that is emitted depends only on the absolute  temperature and not the material of the blackbody. A hotter blackbody emits more photons at all wavelengths than a cooler one.  
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