Optical fiber and reflection experiment
Now, optical fiber is commonly used in homes. Light is transmitted far away on the principle of total internal reflection due to the difference in refractive index.
Experiment 1: Straight light
It is often used to show the straightness of light, and the smoke of incense sticks is put in the container. If you have a spray bottle, you can see better by spraying it and shining a laser beam on it. The floor gets wet though
Experiment 2: Optical fiber principle
When light enters a substance with a large refractive index to a substance with a small refractive index at a large angle of incidence, most of it is reflected. This is called total internal reflection. Since air has a lower refractive index than water, it is total internal reflection when it cannot get out of water. An optical fiber is a device that causes this total internal reflection inside the fiber to prevent light from leaking out.
Experiment 3: Total internal reflection using water and air
It uses water and air to trap light in the water. Attach a straw to the bottom of the PET bottle and let the water run. When you hit the laser from behind, the laser bends along the flow of water.
Attach a plastic tube to the PET bottle as shown on the left and let the water flow. When the laser beam is illuminated from behind the plastic tube, the laser beam cannot go out of the water and travels while totally reflecting in the water. In the photo on the right, the laser beam travels along the water and you can see the red color in the palm of your hand.