The power of a lens is +4D. Find the focal length of

power 4dGiven, 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[ Power Pattern ] Find best premutated 4D numbers based on historical trend.For eg., ABCD=24x, AACD=12x, AABB=6x, AAAB=4x, AAAA=1x Please note that