When light passes through the smoke or dust. It is seen as a beam line And can see through objects Objects that allow light to pass through in a straight line on it. We call this object a transparent material such as glass, air, water, etc. If light passes through an object of some kind, then the distribution of light to ambient light, making a straight line. We call that the object is translucent objects such as paper, glass, plastic panels, etc. The object does not let light through. We called opaque objects such as concrete walls thick cardboard, etc. opaque objects reflect light and absorbs some light, some of them caused by shadows.