An object is placed at a point distant x from the focus of a convex lens and its imge is formed at I as shown in the figure. The distance x, x’ satisfy the relation

An object is placed at a distance x_1 from the principal focus of a lens and its real image is formed at a distance x_2 from the another principal focus. The focal length of the lens is

A point object O is placed at a distance of 20 cm from a convex lens of focal length 10 cm as shown in the figure. At what distance x from the lens should a convex mirror of focal length 60 cm, be placed so that final image coincide with the object?

A point object O is placed at a distance of 20 cm from a convex lens of focal length 10 cm as shown in the figure. At what distance x from the lens should a convex mirror of focal length 60 cm, be placed so that final image coincide with the object?

If an object is placed at the focus of a convex lens, where is the image formed?