Back Focal Length Formula

Equation for calculate back focal length is,

$B F L = \frac{f_{2} (d - f_{1})}{d - (f_{1} + f_{2})}$

where,

f₁ = Focal length of one of the lenses

f₂ = Focal length of the other one of the lenses

d = Distance between the lenses

BFL = Back focal length