The magnification of the image produced by a plane mirror is `+1`. Given reasons.

Explanation

In a plane mirror, object size (h) is equal to image size (h.). Also the object distance (u) is equal to the image distance (v). Object distance (u) is negative, while the image distance (v) is positive. For virtual image, v is + ve
`m=(h.)/(h)=(h)/(h)=+l` or `m=-(v)/(u)=-(v)/((-u))=-(v)/(u)=+l`