Total internal reflection in a stream of water. See video below.
Total internal reflection.
NCEA & Science Curriculum
SCI 1.3, PHYS 1.4, PHYS 2.3
A video is available below, but this demonstration really needs to be done live (see safety notes below). A small hole is drilled in the side of a clear tub. The tub is filled with water and a laser is pointed at the hole from the other side of the tub. The light will follow the water stream to a second tub below.
Download video (right-click an save as): WaterStreamFibreCable (mp4 file, 6 MB)
Usual laser safety, particularly as the room is dark and eyes wide open. Be sure you are using a low-power laser. Dangerous high power lasers have been available on the internet and these should be avoided.
Individual teachers are responsible for safety in their own classes. Even familiar demonstrations should be practised and safety-checked by individual teachers before they are used in a classroom.
Use the light pipes (plastic rods with bends) to illustrate fibre cables. A real fibre cable is helpful is one is available.
Would you like to contribute lesson suggestions? Contact us.
This teaching resource was developed with support from