Use this activity to illustrate light reflection, specifically total internal reflection, as well as how fiber optics work.
The light ray inside the stream of water behaves as it would inside an optical fiber. Optical fiber works like this: you send a light beam into one end of the fiber and it comes out the other end, just as light travels through the stream of water in your experiment. It doesn’t matter if the fiber is straight, curved, or bent into loops; the light beam travels all the way through and comes out the other end. This is called total internal reflection. The light beam bounces around inside the fiber, reflecting back and forth off the walls. It doesn’t pass through the walls and out of the fiber, and it doesn’t stop until it comes out the far end.