Dispersion - Chromatic Abberation

[apples and pears]

Hi all.

I'd like to ask why an achromatic doublet (one concave & and one convex lens of the same curvature cemented together) reduces chromatic abberation.
Do any of you guys know how and why it does this (reduces chromatic abberation)? Thank you.

Just for your info: Chromatic abberation occurs when light passing through a lens is separated into different colours due to dispersion.

[Doc Al]

The chromatic abberations of diverging and converging lenses go in opposite directions.