Editing Cathode ray (section)

===Magnetic deflection===
[[file:Crookes magnetic deflection tube.png|thumb|Crookes magnetic deflection tube]]
The rays path can be deflected by a [[magnetic field]].  [[William Crookes|Crookes]] put a [[magnet]] across the neck of the tube, so that the North pole was on one side of the beam and the South pole was on the other, and the beam travelled through the [[magnetic field]] between them. The beam was bent down, perpendicular to the magnetic field.<ref name="Thomson" />{{rp|150-151}} To reveal the path of the beam, [[William Crookes|Crookes]] invented a tube ''(see pictures)'' with a cardboard screen with a [[phosphor]] coating down the length of the tube, at a slight angle so the electrons would strike the phosphor along its length, making a glowing line on the screen. The line could be seen to bend up or down in a transverse magnetic field. This effect (now called the [[Lorentz force]]) was similar to the behavior of electric currents in an [[electric motor]] and showed that the cathode rays obeyed [[Faraday's law of induction]] like currents in wires. Both electric and magnetic deflection were evidence for the particle theory, because electric and magnetic fields have no effect on a beam of light waves in vacuum.