Air, glass and water lenses in water tank with arc lamp.

Air, glass and water lenses in water tank with arc lamp. A converging lens is placed a focal length away from a carbon arc, producing an intense collimated beam of white light.The beam enters a transparent tank filled with water and fluorescein. Various different lenses are placed by hand into the water and into the path of the collimated beam of light. Because the index of refraction of air is much less than water, the Concave Air Lens focuses light instead of diverging. The Convex Air Lens diverges light instead of focusing. The Convex Glass Lens focuses, but the focal length is longer in water than in air. The Convex Water Lens has no effect at all.