Ray Optics - What is Magnification?

Magnification

The ratio of the size of an image to the size of an object is called magnification.

$M\, =\, \frac {size\, of\, image} {size\, of\, object}\, =\, \frac {image\, distance} {object\, distance}$

$M\, =\frac {I} {O}=-\frac {V} {U}$

magnification for real image is -ve and magnification for the virtual images are +ve

Also

$\frac {1} {f}=\frac {1} {v}+\frac {1} {u}$

$\frac {v} {f}=1+\frac {v} {u}\,$

$\frac {v} {f}-1\, =\frac {v} {u}\,$

$\frac {v-f} {f}\, =\frac {v} {u}\,$

But

$M\, =-\frac {v} {u}=\frac {f-v} {f}$

Further

$\frac {1} {f}=\frac {1} {v}+\frac {1} {u}$

$\frac {u} {f}=1+\frac {u} {v}\,$

$\frac {u-f} {f}\, =\frac {u} {v}$

That is

$M\, =-\, \frac {v} {u}\, =\frac {f} {f-u}$

Post By : Prem Prakash Singh 21 Nov, 2019 2761 views Physics Ray Optics