[OBJ/EM-04004] Plane conductor and a point charge

A charged particle is at a distance \( d\) from an infinite conducting plane maintained at zero potential. When released from rest, the particle reaches a speed \( u\) at a distance \( d/2\) from the plane. At what distance from the plane will the particle reach the speed \( 2u\)?

(a) \( d/6 \)
(b) \( d/3 \)
(c) \( d/4 \)
(d) \( d/5 \)