Table of Contents

**Numerical method in lens**

** ****Lens formula **

**Definition :** The equation relating the object distance (u), the image distance (v) and the focal length (f) of the lens is called the lens formula.

**Assumptions made :**

- The lens is
**thin.** - The lens has a
**small aperture.** - The object lies
**close**to principal axis. - The incident rays make
**small angles**with the lens surface or the principal axis.

*Lens Formula**: *

*Lens Formula*

** ****Linear magnification for lens**

** ****Linear magnification**

**Definition : ** The ratio of the size of the image formed by refraction from the lens to the size of the object, is called linear magnification produced by the lens. It is represented by the symbol m.

If I be the size of the image and O be the size of the object, then

m =

**Power of lens**

** ****u Definition : **It is the capacity or the ability of a lens to deviate (converge or diverge) the path of rays passing through it. A lens producing more converging or more diverging, is said to have more power

Power of lens (in diopter)