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L4-23. Bending Of A Laser Beam In Sugar Solution


To demonstrate a medium with a continually varying index of refraction.


Laser with water tank and sugar.

Setup Time

12 hours. (This demonstration requires overnight to prepare the sugar solution.)




Placing sugar along the bottom of a long, narrow water tank, as the sugar dissolves it creates an index of refraction gradient with the greater index of refraction nearer the bottom of the tank. A laser beam bends continuously in the sugar solution and reflects off the bottom of the tank, as shown in the photograph. Observation of the path of the laser beam is enhanced by adding a pinch of powdered coffee creamer.


William M. Strouse, Bouncing Light Beam, AJP 40, 913, (1972). Pinkston and Crum, Lecture Demonstrations in Acoustics, JASA 55(1), 2-6, (1974).