what is linear magnification?

Linear magnification is ratio of the size of the image to the size of the object.

We know,

Concave Mirror

For Real Image

using sign convention

A^lB^l = -h₂ ; AB = +h₁

PB^l = -V, PB = - u

For Virtual Image

A^lB^l = +h₂ ; AB = h₁

PB^l = +V ; PB = -u

Convex Mirror

A^lB^l = +h_{2 ;} AB = +h₁

PB^l = +v ; PB = -u

Note:

If m>1, image is enlarged.

If m <1, image is diminished.

If m is +ve , image is erect and virtual.

If m is -ve, image is inverted and real.

Other formulae for magnification

or