power 4dA convex lens of power + 6D is placed in contact with a concave lens of power – 4D. What is the nature and focal length of the combination. see full answer. Start JEE NEET FoundationPower ToTo 655. Pick 6 of your favourite numbers from 1 to 55, each bet is RM1. Supreme ToTo 658. Pick 6 of your favourite numbers from 1 to 58, each bet is RM2.