6 7 8. 9 10 12 14 16 18 20 25 30 35 40 50 60 90 



»23 



from LEET (1950); Harvard 

 University Press 



Figure 24. Leet (1950) Presented a Nomogram to Determine the Maximiim 



Thickness of an Intermediate Layer that Existed as a "Blind 

 Zone." The nomogram is entered by any two of the three 

 critical angles involved in a three- layer case (see Figure 

 13 for explanation of critical angle, i^) . From the nomo- 

 gram, a Y factor is determined. The thickness of the upper 

 layer when multiplied by this Y factor yields the maximum 

 possible thickness for a "blind zone." 



3 6 



