In an experiment to prove the existence of the light pressure, two vertically oriented disks are attached as shown to the ends of a horizontal beam in an evacuated tube. The horizontal beam is suspended at its central point by a vertical wire. The surfaces of the disks are simultaneously illuminated by a parallel beam of light of high intensity.
[Figure: Horizontal beam suspended by vertical wire with mirror disk on one end and black disk on other end]
Which explanation best fits the behaviour of the two-disk system?
(a) The horizontal beam is displaced from its equilibrium position due to the equal light pressure on both discs.
(b) The horizontal beam rotates around the vertical wire with the mirror moving in the direction of light propagation and the black disk moving in the opposite direction.
(c) The horizontal beam rotates around the vertical wire with the black disk moving in the direction of light propagation and the mirror moving in the opposite direction.
(d) The experiment cannot show the existence of light pressure because light has no mass.