ABSORPTION OF CARBON 



27 



phyll a and b differ somewhat. In b, the absorption in the blue- 

 violet region covers a somewhat larger region, while in the red 

 portion the area is smaller. 



As the concentration of the chlorophyll increases, the absorp- 

 tion bands become broader and merge one into another (Fig. 10). 

 Finally, there are two absorption bands: one on the right side of 

 the spectrum, covering the red and yellow rays, the other on the 

 left part of the spectrum embracing the blue-violet rays. The 

 green rays and part of the red ones that lie at the very limit of the 

 dark infra-red region can pass without being absorbed. 



700 B 



b, 500 F 



G h4oo 



409 



Fig. 10. — Merging of bands in the absorption spectrum of chlorophyll with increas- 

 ing thickness of the solution layer (after W illslatter and Stoll). 



It is the combination of these two spectral portions which 

 imparts to the chlorophyll the emerald-green color peculiar to it. 

 With further increase in concentration the green rays also are 

 completely absorbed. Finally, only the dark-red rays remain. A 

 very thick layer of a chlorophyll solution is no longer green but 

 cherry red. 



Besides the selective absorption of light energy, chlorophyll 

 possesses another important optical property, fluorescence. In 

 reflected light it appears blood red, due to the fact that a part of the 

 rays falling on it are transformed and reflected with an altered 



