A white board is placed 1 meter away from a helium neon laser. When the shutter of the laser is opened, a circular red spot of diameter 2 mm is observed on the white board. If the white board is moved toward the laser so that it is 0.5 meter away from the laser. Choose the diameter of the beam that is expected on the white board. Consider the divergence of the laser beam. (a) 0.5 mm
(b) 1 mm
(c) 2 mm
(d) 4 mm
(e) 8 mm