power 4d4D History - Check 4D number past winning history since 1985. 4D Number Pemutation. mBox, iBox, i-Perm Source . Date From. Date To. DisclaimerTo find the effective power of a combination of a convex lens and a concave lens, we can follow these steps: 1. Identify the Powers of the Lenses : - The power of the convex lens (P1) is given