A good idea for illustrating refraction is using a laser with some sort of reflective medium in an aquarium. If you've never tried it before, I highly recommend Kalliroscopic fluid... you can find it in your Boreal science supply catalog;
I add about 75-100ml of the fluid to a small aquarium full of water, and then I add some green food colouring just for a "neat" effect...if you don't have Kalliroscopic fluid, a few pinches of flour, starch or chalkdust or some milk will do. The idea is to add particles that the laser light can reflect off of.
Notice the path of the beam compared to the orientation of the laser. The situation changes quite a bit when you raise the laser above the water line...
For the sake of the digital camera, these pictures were taken with the lights on, so I highly recommend doing it a darkened room - students really get a kick out of the glowing beam!
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