NO. 6 EFFECTS OF LIGHT ON ALGAE MEIER 



15 



scale. The intensity measurements are made with a photronic cell 

 and galvanometer systeuL 



A zero adjustment was made with the nutrient solution in the four 

 cells so that there is equal intensity on both sides of the apparatus as 

 shown by the deflection of the galvanometer. It was found that this 

 intensity was practically independent of the depth of the nutrient 

 solution. Then the nutrient solution in the bottom cell on one side 

 is replaced by the freshly inoculated solution at a chosen depth, thus 

 causing a deflection of the galvanometer less than that of the nutrient 

 solution in the cells on the other side. The percentage change in the 

 ratio of the two galvanometer deflections represents the absorption 

 of the inoculated solution. After the experimental period the depth 

 of each culture solution was adjusted to give the same ratio with the 

 nutrient solution as did the original inoculated solution. 



According to Beer's Law, the concentration of the solution is pro- 

 portional to the logarithm of the intensity of the light transmitted 

 through the various thicknesses ; or if the ratio of the light falling on 

 the cell to the light transmitted remains constant, the concentrations 

 of the solutions are inversely proportional to the depth. 



/ = /o(?-°«-" (Beer's Law) 

 where 



I — Intensity of light transmitted by thickness x of nutrient solu- 

 tion plus algae 

 /o = Intensity transmitted by nutrient solution (no algae) 

 (/ and /o are measured with the photronic cell) 

 X = thickness or length of column 

 c = concentration of algae 



== a constant depending on absorbing medium (we assume a is 

 constant for the algae before and after growth in the 

 experiment) 



The procedure was usually to measure the intensity transmitted 

 through the original inoculated solution and to call this h for a 

 length .Vs. Then after growth, .r was adjusted to the same ratio. 



^ = —=k 

 then 



logr -j^ = logr -J— = loge k = K 



