A particle is moving in a circle in front of a plane mirror in the situation as shown in figure. The plane of motion of the particle is perpendicular to the plane of mirror. Then the motion of image of particle with respected to the particle is  

At any instant, the relative velocity between particle and its image parallel to the plane of mirror = 0 i.e. the image does not appear to move parallel to the plane of mirror.

There will be either relative velocity of approach or recession perpendicular to the plane of mirror (approach in the upper part of circle, recession in the lower part) i.e. the image appears to be moving to and fro in a line perpendicular to the plane of mirror as seen by the particle.