OPTICAL METHODS OF BORE-HOLE INVESTIGATION 



333 



improvement in visibility is observed in the infra-red region, such as takes 

 place, for example, in fogs. This has already been theoretically predicted by 

 Shuleikin and Ambartsumyan (^' "^K 



Fig. 4. Dependence of relative intensity of light passing through a suspension, on the 

 thickness h of the layer of suspension and on the angle g). 



Together with attenuation of light in a turbid medium the phenomenon 

 called loss of contrast, which consists of variation of the ratio between the 

 brightness of parts of the object examined is also observed. Loss of contrast 

 is characterized by a coefficient K which is the relative reduction in the ratio 

 of the brightness of the white and dark backgrounds in the presence of 

 a. turbid medium. 



K 



Brl' B , 



100% 



(3) 



