High School Physics

# 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 = h2/h1
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/object distance
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.

Also Read: Magnification of Lens RULES (Summary)

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