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## 05 Mirror Formula and Magnification

#### 5.1 MIRROR FORMULA

The mirror formula gives the relationship between focal length (f) .image distance (v) andobject distance (u) of a spherical mirror.

Mirror formula is represented as:

Where

v = distance of image from pole of the mirror
u = distance of object from pole of the mirror
f = focal length of the mirror

#### 5.2 MAGNIFICATION AND LINEAR MAGNIFICATION PRODUCED BY MIRRORS

Magnification is the ratio of the height of image to the height of object Magnification, m of a spherical mirror can be represented as:

or                =     m    =

$\frac{h2}{h1}$

Where

m = magnification

h2 = height of image

h1 = height of object

The object is always above principal axis and hence h1 is always positive but height of image, h2 may be positive when it is virtual and erect and negative when the image is real and inverted.

#### 5.3 Uses of magnification:

A precision magnifier is a simple magnifier but holds many elements to reduce abnormalities and produce a sharper image.

A water droplet also acts as a magnifier and forms mage of any object behind it.

#### 5.4 Linear magnification:

The linear magnification produced by a mirror is equal to the ratio of the image distance to the object distance, with a minus sign. That is,

Or

Where

m = magnification

u=object distance