n When plane polarized light is incident on the pole of an electromagnet, polished so as to act like a mirror, the plane of polarization of the reflected light is not the same when the magnet is “on” as when it is “off”. It was found that the direction of rotation was opposite to that of the currents exciting the pole from which the light was reflected. (Handbook of chemistry and physics, 52nd edn. Weast RC (ed). The Chemical Rubber, Boca Raton, FL).