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 FoundationUp the stakes with 4D Jackpot, an extension of the orinal 4D game with a multi million ringgit prize! 1. Pick two 4-dit numbers from 0000 to 9999, e.g. (1188, 2288), (3388, 2233), or (1338,