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Magnets have a dramatic effect on cathode rays. View the following images to trace the story of this effect. Click on the photographs on the right.
A cathode ray tube can be used to see the effect of magnets on a cathode ray. Down the centre of the tube is a fluorescent screen to show up the path of the rays.
A collimator is placed at the cathode end of the tube. It contains a slit that narrows the beam of the cathode rays.
This narrows the beam of the cathode rays, as the voltage is increased the beam becomes brighter.
The most extreme deflection occurs when the magnet is close to the beam and the poles are facing outwards. If the south pole is facing out the beams is deflected down. When the north pole is facing out the beam is deflected upwards.
When the poles of the magnet are facing up and down the beam tapers off at the end and fails to make it to the end of the screen. With the south pole facing up the beam is deflected towards the front of the tube.
When the north pole is facing up the rays are deflected towards the back of the screen.
When the poles are horizontal there is little deflection of the rays.
In conclusion, a magnet deflects cathode rays, the closer the magnet the greater the deflection.
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