52 



The Sea-water and its Physical and Chemical Properties 

 Table 18. Absorption coefficient k (cm"^) for pure sea-water 



0-2-0-3 /x according to Kreusler (1901), 0-31 -0-60 /x according to Sawyer (1931) and from 0-7 /n 

 according to Collins (1933). 



Figure 27 shows the spectral range from 0- 1 86 /x to 2.65 /x. From about 0-48 fi towards 

 the red end of the spectrum and beyond, the absorption coefficient increases strongly 

 and continuously. According to the measurements of Aschkinas, weaker absorption 

 bands follow stronger bands between 2-86 /x and 3-27 /x, and at 6-7 ij. where there is 

 almost complete extinction of the radiation. The absorption depends slightly on the 



0-01 



0-5 1-0 I-! 



\ in /i 



2-0 



2-5 



100 



1000 



10000 



Fig. 27. Absorption coeflRcient for pure water (pure sea water for parallel radiation (wave- 

 length range 0-186-2-65 /j.) (From 0-2 to 0-3 ^ according to Kreusler; from 0-31 to 0-60 /u. 

 according to Sawyer; from 0-70 /x on . . . according to Collins). 



temperature and an effect of the salinity has been found but from the summary given 

 by Dietrich it can be seen that the absorption in pure sea-water is almost the same as in 

 pure fresh water. 



The extinction coefficient k takes account of the effects of both scattering and ab- 

 sorption. The scattering of light in a turbid medium is caused by reflection and diffrac- 

 tion of the incident light by the small particles suspended in the medium. If the size 



