relationship beetween image distance, focal length ,power magnification, for both concave and convex lens.​

Object distance means what is the distance between pole and object. Image distance means when image is formed then the distance between pole and image is called image distance. Focal length is the distance between pole and the principal focus of the mirror.

A lens is a clear object, usually made of glass or plastic, which is used to refract, or bend light. Lenses can concentrate light rays (bring them together) or spread them out. Common examples of lenses include camera lenses, telescope lenses, eyeglasses, and magnifying glasses. Lenses are often double lenses, meaning they have two curved sides. A convex lens is rounded outward, while a concave lens curves inward. (A great way to remember this is that a concave lens creates an indent like a cave!)

The image distance can be calculated with the knowledge of object distance and focal length with the help of lens formula. In optics, the relationship between the distance of an image (i), the distance of an object (o), and the focal length (f) of the lens are given by the formula known as Lens formula. Lens formula is applicable for convex as well as concave lenses. These lenses have negligible thickness. It is an equation that relates the focal length, image distance, and object distance for a spherical mirror. It is given as,

1/i + 1/o = 1/f

i= distance of the image from the lens

o= distance of the object from the lens

f= focal length of the lens

Explanation:

Hope it is helpful....