Table 4. --Values of S^, Tp, Tq, and Tq and the resultant detector sensitivity without reference to 

 the spectral energy distribution of a radiant energy source (E\) or properties of an absorbing 

 medium ( Tm) 



Data from manufacturer's published specifications. 

 ^ Data obtained with Beckman Model DU spectrophotometer. 

 ■^ Data obtained with a Gary 14 recording spectrophotometer. 

 ^ Value obtained by graphical interpolation from plot of normalized values from 420-550 m^. 



cosine collector (T;;;) are given. The product 

 at each 10-m/j interval of the four values has 

 been obtained and normalized to 1.00. The 

 maximum transmittance of the detector unit 

 employed in these studies in air is located at 

 490 rcifi with a half -band width of roughly 63 m^u , 

 Next we may consider the effects of E^ and 

 T^. The data of Moon (1940) have beenused to 

 compute the percentage of incident visible 

 radiant energy at the sea surface at intervals 

 of 25 m/i from 387.5 to 712.5 m>i (table 5). The 

 percentage of energy within each 25 m^ in- 

 terval has been assigned to the mean wave- 

 length over that interval. The intervals have 

 been chosen to pernnit the use of Jerlov's 

 (1951) transmission curves (see below). The 

 particular set of data used in this computa- 

 tion (Moon, 1940) refers to an air mass of two 

 (solar altitude 30°). Moon (1940) recommended 



this curve for general use. Reflection at the 

 sea surface, whether selective or nonselective, 

 has been ignored in these calculations. 



The optical-transmittance characteristics of 

 different sea waters for dowawelling irradiance 

 have been conveniently classified into ocean and 

 coastal water types by Jerlov (1951), Since the 

 Jerlov types nnost frequently encountered in this 

 investigation may be characterized as ocean 

 water, we shall proceed to exannine the effect of 

 the selective absorption of Type I, the most 

 transparent, and Type III, the least transparent 

 of the ocean types, upon the effective detector 

 sensitivity. 



From the transmission characteristics of 

 Types I, II, and III ocean water (Jerlov, 1951) 

 (table 9) together with the spectral distribu- 

 tion of visible energy for air-mass -two con- 

 ditions (E^ ), according to Moon, 1940 (table 5), 



10 



