School of Physics Lecture Demonstration Manual

Oe-2 Light Trapped in a Stream of Water

Published: Wednesday 15 March 2006 - Updated: Monday 28 March 2011


To demonstrate how a beam of water may be guided by total internal reflection to follow a curved path in a spout of water.



Click on pictures to enlarge.

Water Light Pipe

Light Trapped in Water Stream Diagram


Water Light Pipe Closeup

Water Light Pipe


This intriguing demonstration of total internal reflection shows how light may be trapped and guided by an unbroken stream of water flowing from a glass jar. A laser beam is initially aimed at the back of a small stopper, through the opposite side of the glass jar. When the stopper is removed the beam is guided by the stream of water and shows up as a brilliant spot where the stream lands. The effect is made visible to a large audience by catching the stream in a large fish tank and inserting a sloping white screen onto which the stream of water splashes.

Safety notes

Electrical safety 

Laser safety 

Sharps safety 


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