Question

meaning of distance equal to focal length ​

Answer 1

Answer:

The focal length of a lens determines the magnification at which it images distant objects. It is equal to the distance between the image plane and a pinhole that images distant objects the same size as the lens in question.

Answer 2

Answer:

if object distance (u) = f then image of object is on Focus

similarly if (v) image distance = f then object is on Focus