Basic optics question - lenses

[jaejoon89]

Why if two concave and convex lenses are nested together, will there be no resulting convergence or divergence if their focal lengths are the same, but if the concave lens has a larger focal length the rays will converge slightly?

What is (are) the mathematical equation(s)/reason(s)?

 

[tiny-tim]

Hi jaejoon89!

"Nested" means that the radii of curvature are the same.

So what mathematical equations are involved?