JSS1 First Term Basic Technology Lesson Note – Basic Emission Theory

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INTEGRATED TOPICS:

Basic Emission Theory

What is emission?

Emission is the displacement or dislodgement of electron from a material with the intention of directing such electron to a predetermined position or object. The basic electronic emission occurs when heat, sunlight, electron collision, electromagnetic field and surface bombardment are used to release electron from the metal surface to the vacuum tube.

Electronic Emission 

The electronic emission is the process of liberating or emitting free electrons from the metal surface to the vacuum tubes. A vacuum tube is an empty tube in which the air has been completely removed for the purpose of storing liquefied gas.

Methods of Emission

There are four principal methods of liberating electron from the surface of metal:

1. The thermionic emission
2. The photo-electric emission
3. The cold-cathode emission
4. The Secondary emission

The Thermionic Emission: The thermionic Emission is the method by which free electrons are emitted from the surface of a metal by the application of heat energy. Another name for thermionic emission is THE PRIMARY EMISSION.

The Photo-Electric Emission: This is the method by

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