The idea that static magnetic fields might have a therapeutic value has been around for centuries. A

Question:

The idea that static magnetic fields might have a therapeutic value has been around for centuries. A currently available rare-Earth magnet that is advertised to relieve joint pain is shown in figure. It is 1.0 mm thick and has a field strength of 5.0 x 10^?2 T at the center of the flat surface. The magnetic field strength at points away from the center of the disk is inversely proportional to h 3, where h is the distance from the midplane of the disk. How far from the surface of the disk will the field strength be reduced to that of Earth (5.0 x 10^?5 T)?