A convex lens has the focal length of 2.8 mm. If a candle is placed at the distance of 20.0 cm in front of the convex lens and makes a horizontal displacement of -0.5 cm (i.e. toward the lens along optical axis), what is the horizontal displacement made by its image behind the convex lens? A coordinate system OXY is vertically placed on a horizontal surface. A light source is placed at (0.0, 10.0) (cm) which emits a single light ray toward the location at (20.0, 0.0) (cm). The reflected light ray could be seen at: