A 1:1 solution of Karo syrup and water is left to sit overnight.
The syrup slowly sinks to the bottom and a varying level of index
of
refraction results. About 2 inches of syrup on the bottom looks
good for this demo. A laser is shined into one end of the
plexiglass tank,
and it is seen to bend because of the varying index
of refraction from the bottom to the top layer.
When the beam hits the bottom of the tank, it reflects back up,
then curves down again, making it appear that the beam is
bouncing.
This demonstration is difficult to set up, and ample time should
be allowed for it to be set up properly. This requires at least a
day in advance so that the water and syrup can sit overnight.
Location: