Demonstration Description: This one is nice. Trust me.
The total internal reflection of a helium-neon laser beam within a water tank is demonstrated. The angle of incidence can be varied and the phenomenon observed as one passes through the critical angle.
Used in the same tank as N3 Refraction in Water
Point the red laser from below the tank to show the point of internal reflection
Move the laser back and forth to show where the point of internal reflection is