Question

An object is placed 20cm from a converging lens if the real image formed is 80.0cm from the object, the focal length of the lens is ?

Answer 1

• According to the convex lens formula, $1/f=1/u+ 1/v$ where f is the focal length, u is the object distance while v is the image distance.
• 1/f=1/20+1/80 which gives 1/16
• The focal length of the lens would therefore, be 16cm.