Reflection and Refraction with a Fish Tank

PIRA 6A42.20

Mix enough powdered milk or Pine Sol into the water of a fish tank to make the water slightly opaque.  Shine a laser on the water to illustrate refraction.  The incident and reflected rays can be made visible (as in the picture at top right) with chalk dust from two erasers slapped together, or with the smoke from the Dyno-Fog smoke machine shown at bottom right.  Refraction of the transmitted light as it leaves the water and returns to air (via glass) can be seen on the far side of the fish tank if sufficiently large angles of incidence are used at the top water-air surface.