Magnifying Lens In Water
To show that the focal properties of a lens depend on the medium in which the lens is located.
Lens-fuse box assembly, water tank.
A small fuse box is mounted on a holder at a distance less than the focal length behind a convex lens, so the lens acts as a magnifying glass. Note, in the photo at the left, the magnification of the fuse box when the system is in air. Then dip the entire lens-object system into water. Because there is much less bending of the light at the water-glass interfaces than at the air-glass interfaces, the magnification is much less.