When an object is at a distance 3 meters and 1meters from the optical centre of a convex lens, a real and virtual image are formed respectively, with the same magnification. Find the focal length of the lens (in meters)

When an object is at a distance u_(1) and u_(2) from the optical centre of a lens, a real and virtual image are formed respectively, with the same magnification.The focal length of lens is:

When the object is at distance mu_1 and mu_2 from the optical centre of a convex lens, a real and a virtual image of the same magnification are obtained. The focal length of the lens is

When the object is at distance u_1 and u_2 from the optical centre of a convex lens, a real and a virtual image of the same magnification are obtained. The focal length of the lens is

When an object is at distances x and y from a lens, a real image and a virtual image is formed respectively having same magnification. The focal length of the lens is

When an object is at distances x and y from a lens, a real image and a virtual image is formed respectively having same magnification. The focal length of the lens is

When an object is at a distance u_(1)andu_(2) from a lens, real image and a virtual image is formed respectively having same magnification. The focal length of the lens is

When an small object is placed at a distance x_(1) and x_(2) from a lens on its principal axis, then real image and a virtual image are formed respectively having same magnitude of transverse magnification. Then the focal length of the lens is :

When an small object is placed at a distance x_(1) and x_(2) from a lens on its principal axis, then real image and a virtual image are formed respectively having same magnitude of transverse magnification. Then the focal length of the lens is :

The distance between an object and its real image formed by a lens is D. If the magnification is m , the focal length of the lens is