Practice portal › Dual Nature of Matter and Radiation › Electron Emission and Cathode Rays
Asked in AIPMT 1988 · Cathode rays, thermions and the electron
Heating a metal gives its conduction electrons extra thermal energy.
Some gain more than the work function and escape from the surface, exactly as photoelectrons do when given energy by light.
This is thermionic emission, and the escaping particles are called thermions.
They are simply electrons, which is why a heated filament serves as the electron source in a cathode-ray tube or an electron gun.
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