A beam of light gets reflected from a plane mirror and a real image is formed. The incident beam should be
Plane mirrors don't usually form real images They form virtual images of real objects. However, things can be arranged so that a plane mirror does form a real image. A convergent light beam can do this. So the answer is "convergent"
When at convergence point, a convergent beam of light is incident on the plane mirror, a real image is formed at the point