The availability of high-field rare earth magnets allows us to observe the diamagnetism of water. To easily demonstrate this, a 12-mm NdFeB cube magnet,⁶ with a pole end facing up, is covered by about 1 mm of water. Since the diamagnetism of water causes it to be repelled by the magnetic field, a square concave dent appears on the surface (Fig. 3). The trick to making this visible is placing some flat black paper (emery paper works well) over the magnet, reducing reflections other than from the water's surface. By focusing on bright reflections, the concavity on the surface above the magnet is quite evident.

Figure 3.

Author's Note: Certain commercial materials are identified in this paper. Such identification does not imply recommendation or endorsement by NIST or by the U.S. government, nor does it imply that the materials identified are necessarily the best available. The paper is not subject to copyright.