20 



PHOTOCHEMICAL PRINCIPLES 



400 4S0 SOO 550 600 



Wavelength, m/x 



«50 



700 



750 



Fig. 3. Bottom curve, absorption spectrum of a Chlorella suspension 

 measured with the Beckman DK2 recording spectrophotometer using opal 

 glass plates. Top curve, the same without opal glass. Middle curve, light 

 scattering at 90° from another Chlorella suspension (Latimer, 1957). 



tion is seen by comparing tlie top curve witii that for the middle 90° 

 scattering curve, and for the absorption alone given by the bottom 

 curve. 



Dr. Latimer also investigated the effect of the angle of light gathered 

 by the photocell in a spectrophotometer on the apparent absorption 

 spectra of cellular suspensions. With his apparatus it was possible to 

 measure the absorption spectrum of a cellular suspension for a highly 

 coUimated narrow beam and to compare this measurement with the 

 spectra measured through annular rings subtending different angles. 

 The results of a series of such measurements are shown in Fig. 4. In 



