(1)/v + (1)/u = (1)/f (1)/v + (1)/15 = (1)/5 (1)/v = (1)/5 - (1)/15 = (3 - 1)/15 = (2)/15 ∴ v = (15)/2 = 7.5 cm magnification = (v)/u = (image size)/object size (7.5)/15 = (X)/4 ∴ image size. X = (7.5 x 4)/15 = 2 cm
