58 



The Sea-water and its Physical ami Chemical Properties 



The relationship between the intensities of the incident and the reflected radiation is 

 expressed by Fresnel's law. If 7 is the intensity of the incident radiation and R that 

 of the reflected radiation, the relationship between them is given by 



R 

 J 



sin^ (/ — /■) tg^ (i 



r) 



sin2 (/ + /-) tg^ (/ + /-) 



Ify = 100 and n == 1-333 this gives the values shown in Table 23. If the angle of inci- 

 dence is 0°, only 2% of the radiation is reflected and almost the whole of the energy 

 penetrates through the surface. 



Table 23. Reflected radiation R and refracted radiation Dfor different angles of incidence 

 i of radiation on a water surface {J = 100, n = 1-333) 



With increasing angle of incidence the reflected energy increases only slowly up to 

 about / = 60^ and thereafter very rapidly. The larger the angle of incidence the more 

 is reflected, at 70° more than 13%, at 80° more than 35%. This is shown in Fig. 32. 

 The rays coming from the upper left incident on the surface are split into reflected and 



10° f 



Fig. 32. Graphical representation of the proportions of reflected and transmitted radiation 



incident on the surface of water at different angles. For each ray incident from the upper 



left with an intensity of 100 there will be a reflected ray and a ray transmitted into the water. 



Both are represented by vectors which give the intensity and the direction of the ray. 



entrant rays; the incident rays have an intensity of 100 and the vectors marked on the 

 diagram correspond in intensity and direction to the reflected and entrant rays. Larger 

 values for the reflected energy only occur with obliquely incident light and especially 

 in that range, where the entrant radiation falls to very low values. It can be seen that 



