As described earlier, the signal is completely reflected at time location tb. Thus, the signal travels twice the thickness
of tungsten T2 from point Va to point Vc without an R loss at time location tb. Using equation (8), such that Vi is
equivalent to (1-R)Va, Vf is equivalent to Vc, and d is twice the thickness of tungsten T2, we derive an expression for
2 from equations (9-14) as a function of measurable voltages V1 and V2.