Variable index of refraction: laser beam bends in water tank with sugar.

Laser beam bends in water tank with sugar added. An even layer of granulated sugar, about a centimeter thick, is placed on the bottom of a small water tank. Water is slowly added by dribbling from a hose that is constantly moved over the surface, to cause minimum disturbance of the sugar. The tank is left undisturbed for 48 hours. The sugar slowly dissolves, forming a solution with a gradient of refractive index. A laser beam shown down the length of the tank will be bent. If there is no undissolved sugar left on the bottom of the tank, the beam can be adjusted so that multiple bounces can be seen down the length of the tank. The 5 mw green laser pointer is the best laser to use to see the beam within the tank. It is best seen in a darkened room. (This effect is similar in principle to a mirage. A mirage is an optical illusion often seen in a desert. Light rays refract as they pass from cool air down to hot air near the ground. Sometimes there appear to be pools of water on the hot highway in the distance, which disappear as one approaches. What looks like water is refracted light from the sky and clouds, bent downward. Sometimes distant objects appear closer or distorted, etc.)