The motion of light in a straight line. Rays of light to give in to tell which direction the light move using the arrow directed straight to dictate direction.
Vertical movement of light in a straight line. A ray of light will help to ease the movement direction of the light by using the arrows on the line to tell direction.
The movement of the light in a straight line. A ray of light to allow ease of directional light moving using arrows directed on the straight lines to tell the directions.