An object is placed in front of a converging lens at a distance greater than twice the focal length of the lens. The image obtained is:

Q. If an object is placed $25cm$ in front of the converging lens forms an image $20cm$ behind the lens, then what is the focal length of the lens ?

Q. For an object placed at a distance $20cm$ in front of a convex lens, the image is at a distance $20cm$ behind the lens. The focal length of convex lens is:

Q. At what distance should an object be placed in front of a convex lens of focal length $10$ cm so to obtain an image twice the size of object ?

Q. An object is placed in front of a converging lens. The lens has a focal length f. The lens produces a real, enlarged image of the object. ​
In which labelled position is the object placed?

Q. An object is placed in front of a converging lens at a distance equal to twice the focal length $f_1$ of the lens. On the other side of the lens is a concave mirror of focal length $f_2$ separated from the lens by a distance $2(f_1+f_2)$. Light from the object passes rightward through the lens, reflects from the mirror, passes leftward through the lens, and forms a final image of the object.