PURPOSE: Demonstrate internal reflection and dispersion of light in formation of a rainbow.

DESCRIPTION: A single light ray is focused by a convex lens to limit its width. The ray enters a plastic disc, which models the water drop, is reflected internally and returns at an angle of about 40 degrees. The dispersion is apparent at a distance from the drop, so the light can be cast on a wall or a distant screen to see the colors. The photographs above show the light ray as it passes through the plastic disc "water droplet" and a close-up of the dispersion as it occurs on a small screen to the upper left of the droplet - the bright line in the photograph at the left.

SUGGESTIONS:

REFERENCES: (PIRA 6A46.30)

EQUIPMENT: Optical board with single ray baffle, convex lens, and plastic disc. Optical Board Configuration

SETUP TIME: 5 min.