Table 156 



ABSORPTION OF RADIATION BY PURE LIQUID WATER 



445 



The decrease in intensity of a parallel beam of radiation of wave length X (i.e., of a 

 small wave-length interval in the neighborhood of X) in the direction of the beam by 

 passing through a slab of pure water of thickness x is expressed by 



h = Ue-** 



where /ox is the intensity of the beam entering the slab and h the intensity after passing 

 through the slab. k\ is called the absorption coefficient. The termabsorption refers here 

 to the depletion of energy both by absorption and scattering. 



There is disagreement among various investigators as to the values of k\ for pure 

 water. The values presented here are those summarized by Dietrich ' from the following 

 sources : 



0.310 to 0.650, W. R. Sawyer, Contr. Canadian Biol. Fish., vol. 7, p. 73, 1931. 

 0.700 to 2.650, J. R. Collins, Phys. Rev., vol. 26, p. 277, 1925. 



Dietrich also indicates the results of other investigators. 



The temperature dependence of the absorption produces an increase of about 0.5 percent 

 in k\ for every 1 °C. rise in temperature in certain portions of the infrared near 0.73/x, 

 but over a large portion of the spectrum is much smaller. The values ascribed to Collins 

 have been interpolated by Dietrich for 18 °C. He also notes that the effect on the 

 absorption coefficient of the presence of dissolved salts in the concentrations found in sea 

 water has been found to be negligible. 



1 Dietrich, G., Ann. d. Hydrogr. u. Mar. Meteorol., vol. 67, pp. 411-17, 1939. 



ABSORPTION OF RADIATION BY PURE LIQUID WATER 



SMITHSONIAN METEOROLOGICAL TABLES 



