It has been observed that a mirror always forms the image between...

For a spherical mirror, the mirror formula is given by $\dfrac{1}{v} + \dfrac{1}{u} = \dfrac{1}{f}$.

For a real object placed in front of the mirror, the object distance $u$ is negative. Let $u = -x$ where $x > 0$.

For a convex mirror, the focal length $f$ is positive. Substituting $u$ into the mirror formula gives:

$\dfrac{1}{v} - \dfrac{1}{x} = \dfrac{1}{f}$

$\dfrac{1}{v} = \dfrac{1}{f} + \dfrac{1}{x}$

Since both $f$ and $x$ are positive, $\dfrac{1}{v} > \dfrac{1}{f}$.

This implies that $0 < v < f$.

Thus, the image distance $v$ is always positive and less than the focal length $f$. The image is always formed behind the mirror, between the pole and the principal focus, irrespective of the object's position.

A plane mirror forms an image at the same distance as the object, and a concave mirror can form images beyond the focus or even at infinity depending on the object distance.

Answer: It is a convex mirror.