An object of size 10 cm is placed in front of a convex lens of focal length 20 cm. Find the size of the image formed.
Solution
Object of size = 10 cm Focal length = 20 cm From lens formula = 1/v- 1/u = 1/f 1/v + 1/10 = 1/20 1/v = -1/20 v = -20 cm Hence, magnification = v/u = 2 Therefore, the image formed is virtually erect and magnified two times.