What does positive magnification mean?

An object,$4.0 \, cm$ in size,is placed $25.0 \, cm$ in front of a concave mirror of focal length $15.0 \, cm$. At what distance from the mirror should a screen be placed in order to obtain a sharp image? Find the nature and the size of the image.

Where is the image formed when an object is placed between the principal focus $(F)$ and the center of curvature $(C)$ of a concave mirror?

At what position should an object be placed in front of a concave mirror to obtain a magnification of $(- 2)$?

The image formed by a lens is due to which optical phenomenon?

If the angle of incidence on a plane mirror is $30^{\circ}$,what is the angle of reflection (in $^{\circ}$)?