Double Lens System Calculator

Lens 1 Focal Length (f₁) Lens 2 Focal Length (f₂) Lens Separation (d)

Input Parameters:
f₁ = Focal Length of Lens 1
f₂ = Focal Length of Lens 2
d = Distance Between Lenses

[Double Lens Diagram Placeholder]

$$ \frac{1}{f_{eq}} = \frac{1}{f_1} + \frac{1}{f_2} - \frac{d}{f_1 f_2} $$

$ f_{eq} $ = ?

Output Parameter:
f_eq = Equivalent Focal Length