CBSE Class 10 Science 2017 · Paper 31/2/2 · Question 16

The object is placed 35 cm in front of the lens ($u=-35$ cm), on the other side from the image — that is, at $2F_1$, with the image at $2F_2$. The lens is convex (converging), with focal length $f=+17.5$ cm. When the object is moved 20 cm towards the optical centre it is 15 cm from the lens ($u=-15$ cm), inside the focal length. The image is then formed 105 cm from the lens on the same side as the object ($v=-105$ cm); it is virtual, erect and magnified 7 times ($m=+7$). The ray diagram shows the two emergent rays diverging, with their backward extensions meeting at the image.