LIGHT ABSORPTION OF PHOTOSYNTIIESIZING CELLS 



63 



apparatus has appeared.) Probably lilters were used to prevent ex- 

 citing light from reaching the multiplier. 



Description of a complete apparatus. A diagram of the apparatus 

 used by us in recent investigations (5,7,8) is shown in Fig. 1. It is a 

 modification of one described before (1). A monochromatic beam is 

 split into two beams by means of a rotating disc consisting of mirrors 

 alternating with holes. The beam passing through the holes in the disc 



TO B o- 

 TO C O- 



CAPACITORS IN /J F 



K = X 1000 M = X 10* 



Fig. 2. Amplifier and phase- and ffefiuency-sen.sitive rectifier. 



is the measuring or scanning beam. This beam passes the movable wire 

 screen C and the suspension. The compensating beam bypasses the 

 suspension and causes a deflection of the recorder opposite to that of 

 the scanning beam, keeping the indicator of the recorder on scale. 

 The intensity of the compensating beam can be adjusted by means 

 of a "wedge." In many experiments the intensity of the scanning beam 

 and sensitivity setting of multiplier and amplifier was such that a 



