# Magnification Produced by Lenses

Last updated on June 22nd, 2023 at 04:19 am

In this post, we will define the **Magnification produced by Lenses**, and then see the formulas used to find the magnification. There are 2 ways to define and formulate the term “Magnification by Lenses”.

We will study both sets here in this post.

## Magnification produced by Lenses [based on image and object size]

We will now write 1st version of the definition and formula for the magnification produced by a lens in terms of the image size and object size.

**Definition of Magnification by Lens [size based]**

The size of the image relative to the object is given by **linear magnification**. Linear magnification is the ratio of the height of the image to the height of the object.

**Formula of Magnification by Lens [size based]**

Magnification = height of image/height of the object.

or, m = h_{2}/h_{1}

where m = magnification

h2 = height of the image

and h1 = height of the object

The size of the image formed by a lens depends on the position of the object from the lens. For example, the image formed by a convex lens can be smaller than the object, equal to the object, or bigger than the object.

## Magnification produced by Lenses [based on image and object distance]

We will now write 2nd set of definition and formula for the magnification produced by a lens in terms of the image distance and object distance.

**Definition of Magnification by Lens [distance based]**

The linear magnification produced by a lens is equal to the ratio of image distance to the object distance.

**Formula of Magnification by Lens [distance based]**

Magnification by lens = image distance/objectdistance

or, m = v/u

where m = magnification

v = image distance

and u = object distance

## Magnification by Convex Lens versus Magnification by Concave lens

If the magnification m has a positive value, the image is virtual and erect. And if the magnification m

has a negative value, the image will be real and inverted.

Since a convex lens can form virtual images as well as real images, therefore, the magnification produced by a convex lens can be either positive or negative.

A concave lens, however, forms only virtual images, so the magnification produced by a concave lens is

always positive.

A convex lens can form images which are smaller than the object, equal to the object, or bigger than the object, therefore, the magnification (m) produced by a convex lens can be less than 1, equal to 1, or more than 1. On the other hand, a concave lens forms images which are always smaller than the object, so the magnification (m) produced by a concave lens is always less than 1.