Question

When does a plane mirror form a real image

Answer 1

A plane mirror always form virtual images of real objects

as here for any real object which is kept to the left of mirror image is always formed on the right of the mirror and since images formed on the right of the mirror are always virtual ,hence plane mirror always forms virtual images of real objects.

But for the virtual objects the case is just reversed because the a virtual source always produces converging rays which after reflection actually meet at a point on the left of the mirror and hence forming real image.