Two point objects A and B are placed on the principal axis of a convex lens of focal length 20 cm . The objects are at distances of 10 cm and 30 cm from the optical centre, on the same side of the lens. The distance between the images formed by the lens is:

Step-by-step solution

Using the lens formula, 1 v - 1 u = 1 f For object A ( u_A = -10 cm ): 1 v_A - 1 -10 = 1 20 1 v_A = 1 20 - 1 10 = - 1 20 v_A = -20 cm The image of A is virtual and forms 20 cm from the lens on the same side as the object. For object B ( u_B = -30 cm ): 1 v_B - 1 -30 = 1 20 1 v_B = 1 20 - 1 30 = 1 60 v_B = +60 cm The image of B is real and forms 60 cm from the lens on the opposite side. Since the images are on opposite sides of the lens, the distance between them is the sum of their distances from the optical centre