Emission of Electron and Work Function

We all have seen the glowing bulb.

And we all might have noticed the filament inside the electric bulb.

When we do the switch ON then within seconds the electric bulb starts glowing.

The filament has a property called resistance. Therefore, when the electricity passes the filament it heats up and starts glowing.

When the filament heats up, the electrons are emitted from the surface of filament metal and this process is called electronic emission or emission of electrons.

Let’s discuss the emission of electrons and work function.

Emission of electron is the liberation of electrons from the surface of metal.

The atom has the two entity: (a) nucleus, (b) electrons.

The nucleus is positively charged and the electrons are negatively charged and revolves around the nucleus in orbits.

There are many orbits in which the electrons are revolving and electrons which are very close to the nucleus are strongly attracted by the nucleus with high energy.

Because, the unlike charges attracts each other and the electrons which are strongly attracted are called bound electrons.

And the electrons, which are far away from the nucleus, are weakly attracted with low energy. So, this type of electrons are called free or conduction electrons.

The number of bound electrons and free electrons are vary from metal to metal.

And the number of free electrons are more in comparison to the non-metal.

Let’s assume a particular metal which has numerous number of atoms . That means they are having so many number of free electrons.

Now these electrons are having the sufficient energy to jump from one atom to another atom.

But they are not capable to move out from the surface of the metal.

Now, after getting some more energy, these electrons can move out from the surface and this process is called emission of electrons.

Let’s discuss the term called work function.

Work function is the minimum energy that we require to supply to free electrons to move them out from the surface of the metal.

The typical work function will vary from to the .

And the value of work function depends upon the nature and purity of the metal.

Work function depends upon the nature of the metal, means how many numbers of electrons are present in the metal.

And work function also depends upon the purity of the metal, means if the metal is pure then the work function will be different.

And if the metal is impure then the work function will be different.

Hence, after getting sufficient energy, electrons can leave the surface of a metal.

Revision

The electrons closer to the nucleus is with high energy and the elctrons far away from the nucleus is with low energy.

And, after getting the sufficient energy, the outermost orbits electrons can move out from the surface and this process is called emission of electrons.

Work function is the minimum energy that we required to supply to free electrons to move out from the surface of the metal.

The value of work function depends upon the nature and purity of the metal.

The End