CoachTo draw light, physicists use the light ray: a straight line with an arrow, showing one thread of light and the way it runs. A torch beam is drawn as a fan of rays; a thin laser beam as a single ray. Like the force arrow, the ray is a little drawing that carries a law inside it: light’s roads are ruler-straight.
Examples
Example 28.3 (Where the law shows itself)
Once you know the law, you see it everywhere: the straight sunbeams through mist or blinds; the sharp straight edge of a torch beam in dusty air; the laser pointer’s dead-straight thread; and every lighthouse sweeping straight blades of light across the night sea. Bent light is never seen — fountains and forests may curve, light will not.