Chapter-9|Ray Optics and Optical Instrument|NCERT 12th Physics:
Thin Lens Formula:
It is a relation between focal length of a lens and distance of object and image from optical centre of the lens.
Let O be the optical centre and f be the principal focus of a convex lens of focal length OF= f,
Distance of object OB= u
Distance of image OB’= v
Note: This formula can also be approved for concave lens and for virtual image in the same way.