Consider a magnetic ball falling through a copper pipe. It falls slower than it would if it wasn't near any copper. We can use this to determine that the closer a magnetic ball is to copper, the slower it falls.

Now lets have a magnetic ball falling past a copper block. The side closer to the copper block is moving slower than the other side. It should start spinning as a result. Ignoring air friction and the Magnus effect, would the ball's path curve around the copper block(similarly to how a photon diffracts)?

  • $\begingroup$ My unauthoritative guess is that the eddy currents induced in the block would have at least some component opposing the balls' magnetic field in a lateral direction, pushing it away. Darned if I'd commit to that in a court of law, though. $\endgroup$ Nov 22, 2015 at 21:18
  • $\begingroup$ Diffraction of light is a different phenomenon than a ball being deflected by magnetic forces around an object. Photons are behaving according to wave diffraction rules when going through a slit or around an obstacle. $\endgroup$
    – Peter R
    Nov 23, 2015 at 2:39
  • $\begingroup$ @PeterR I know they are different phenomenon. Hence why I used the quotation marks. I was just curious if a particle(such as a magnetic ball) could act like a diffracting wave. $\endgroup$
    – Laff70
    Nov 23, 2015 at 4:57

1 Answer 1


Can a magnetic ball “diffract” around a metal object?


An eddy current separator (see the picture) works on this principle. The difference is that the magnet there can not have a translation movement. It is the nonferrous object the one wwhich is deflected. However, according to Newton's third law, the same force that deflects the nonferrous materials also acts on the magnet which would have been pushed in a certain direction had it not been held on place.



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