An infinitely long rod lies along the axis of a concave mirror of focal length f. The near end of the rod is distance `u gt f` from the mirror. Its image will have length

An infinity long rod lies along the axis of a concave mirrror of focal length f.The near end of a the rod is at a distance ugtf from the mirror ,Its image will have a length:

For a concave mirror of focal length f, image is 2 times larger. Then the object distance from the mirror can be