4D X HAPPY POWER

power 4dA convex lens of power 4D is kept in contact with a concave lens of power 3D, the effective power of combination will be . View Solution; Knowledge Check. A convex lens of focal length 40 cmGiven, Power of convex lens=4D. Placed at 40 cm from a wall. To Find, Distance of a candle. Solution, It is given that ,Power = 4D. Then, P = 1f. So, 4 D = 1f