What is Electron Emission and Emission types

In my last post, i talk about the role of electronic technology in our daily life and its importances, and this is our second post about electronics. In this post i am writing about Electron Emission and its types with big try to explain it with you in sample words.
In this post we will disuse the following topics:

• What is Electronic Emission?
• Thermionic Or Primary Emission
• Secondary Emission
• Photo Electric Emission
• Field Emission

What is Electron Emission?

In Simple words, " The phenomenon of escaping or emitting electrons from the metal surface into surrounding by applying a specific energy is called the Electron emission.

In other words applying a specific method or force on specific metal for emitting electrons or getting electrons is called Electron emission.

We know that every metal is made form those atoms which are conjunct doggedly with one anther in the shape of Crystal.

We also know that electron which separate form atom outer shell electron is called atom free electrons, note that due to these free electrons flow the current flow is possible in wires, transistors and valves.
An every conductor free electrons are moving or surrounding- in atom outer shell electron, These free electrons are not emitting himself from metal surface because the metal surface force stop escaping electrons on normal temperature.
Its mean that with out applying force the free electron not escaping from metal.
When we provide some extra energy, the electron absorb the energy and due to this observation its kinetic energy become in cress and free electron able to emit form metal surface. This emitting is called electronic emission.

this image is take form an online pdf book

Types Of Electron Emission

For Escaping electron from any conductor or metal we use 4 different methods which are below.

Thermionic - Primary Emission

The method of Electron emission we use more then other methods of emission. In this method we provide the heat to metal for emitting free electron form metal surface, due to temperature, the free electron kinetic energy and thermal energy in cress and electron start escaping from the metal surface. If you provide more temperature, the electron will emitting more, its means that temperature increasing and decreasing have a big link with electrons.
This method of emission is just like liquid evaporation method.
Also Read
Introduction to Electronics technology - Beginners Guide

Secondary Emission :

When a moving particle bombardment on metallic surface and provide maximum- energy to make free electrons able to broke the energy bears- for escaping is called secondary emission.
In other words in this method high velocity electrons bombardment on cathode to make escaping electrons form cathode. This method called secondary emission of electrons.

Photo-Electric Emission

In this method the E mission is done by providing the light energy. In this type of emission we provide light or we do lighting on specific metal surface, the light energy transfer to the metal internal free electrons, due this the elect ron kinetic energy or speed in cress of electrons and its start escaping form metal. This type of electron emission is called photo electric emission.

Field Emission

We also called cathode emission to field emission. We also know that electron are negatively charge particles- and when we provide the high positive field to electrons, the electrons gets compatible energy and its able to discharge.
Or
Use a strong magnetic field for emitting electron is called field emission.