Answer:
Dr Munetaka Tanaka  kindly answered above question.
 
  
A body such as Sun is aggregation of atoms and molecules, and they interact with one another. The type and scale of the interaction wobble with time, so energy levels also wobble. Since there are countless numbers of the atoms and molecules, radiation energy from a body becomes continuous. In the case of molecules, since vibrational level and rotational level also wobble, the spectra easily become continuous.
 
In the emission from hydrogen discharge lamp (Balmer’s experiment), for example, the spectrum is discontinuous when pressure in the lamp is extremely low. But the spectrum become more continuous as the pressure is increased. Do you know that deuterium lamp is used as the light source of UV spectrophotometer? This lamp is used as the continuous light source.
 
 
Acknowledgement
Dr. Munetaka Tanaka
He is studying photoreaction of organic molecules. He is also applying this study to research about reaction mechanism of environmental pollutant, and to synthesis of new compounds.
 
 

This article is translated by Chemistryquestion.com from the original article in Chemistryquestion.jp.  Please let us know if you find any errors.