Focal Length, Radious, Magnification, Power of Lenses

Convex Lense(Converging Lense) - Surfaces are Convex towards rarer medium.
Concave Lense(Diverging Lense) - Surfaces are Concave towards rarer medium

Focal Length of Lenses

1) f = $R~^1 R~^2 #_ (n-1)(R~^2 +R~^1 )

R - Radii of curvatures n - Refractive Index of Lense

2) f = $uv #_u+v

u - Object Distance. v - Image Dist.

Note: If given lense is equiconvex lense, then
R~^1 = R~^2 = R and f = $R#_2(n-1)
$ => n = 1 + $R #_2f