A plane mirror $M$ is arranged parallel to a wall $W$ at a distance $l$ from it. The light produced by a point source $S$ kept on the wall is reflected by the mirror and produces a light spot on the wall. The mirror moves with velocity $v$ towards the wall. Then

 

the spot of light will move with the speed $v$ on the wall

the spot of light will not move on the wall.

as the mirror comes closer, the spot of light will becomes larger and shift away from the wall with speed larger then $v$.

the size of the light spot on the wall remains the same.