The Cathode Ray Tube

The Cathode Ray Tube

Cathode rays are streams of high speed electrons moving from the cathode.

How a Cathode Ray tube works:

  • A low voltage is placed across the filament. Current flows through and it becomes white hot, this heats the cathode.
  • Thermionic emission occurs at the cathode. Electrons are emitted.
  • There is a large voltage between the anode and the cathode. The anode is positive with respect to the cathode. The electrons from the cathode accelerate towards the anode. They can get up to great speeds as they are not opposed by gas molecules as there is a vacuum.
  • They go through the hole in the anode and go to the end of the tube.
  • At the end of the tube there is a screen coated with fluorescent material, when the electron strikes the screen, its kinetic energy is converted into light energy.

Cathode Rays

  • They cause certain substances to give off light when they are struck. (e.g. Zinc Sulphide)
  • They have kinetic energy.
  • They can be deflected in electric and magnetic fields.
  • They are invisible but their presence can be detected in a tube by making them strike fluorescent material.

The Electron – Physics Chapter Summary →

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