A virtual image that is twice the size of the object is created using a concave mirror with a focal length of 20 cm. Identify the object's distance from the mirror.

Magnification (m)= 2
Focal length (f)= 20 cm
Object distance(u) = ?

Magnification formula for spherical mirrors:
$\mathrm{m}=-\frac{\mathrm{v}}{\mathrm{u}}=+2\Rightarrow \mathrm{v}=-2\mathrm{u}$

Mirror formula:

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

$\therefore \frac{1}{\mathrm{u}}+\frac{1}{-2\mathrm{u}}=\frac{1}{-20}$

$\Rightarrow \frac{1}{2\mathrm{u}}=\frac{1}{-20}$

$\Rightarrow \mathrm{u}=-10 \mathrm{cm}$

Therefore, the object's distance will be -10 cm. The negative sign signifies that the object is placed on the left side of the mirror.