Question

What is called the magnification of an image ? Derive the fonnula of magnification for spherical lens.Answer the given question in brief.

Answer 1

Magnification of an image is defined as the ratio of the height of image to the height of object.
Magnification (m) =$\frac{\text{image height}}{\text{object height}}$

in the figure , we can easily see that
∆ABO and ∆A'B'O are similar
so, $\bf{\frac{A'B'}{AB}=\frac{OB'}{OB}=-\frac{v}{u}}$-------(1)

from definition of magnification
magnification , m = A'B'/AB = -h'/h ----(2)

from equations (1) and (2),
magnification for lens = v/u

Answer 2

Magnification of an image can be defined as the ratio of the size or height of the image to the size of the object.

It is denoted by m.

Derivation is given in Attachment !