Electron beamsQ)What is thermionic emission?

When a cathode is heated electrons are emitted from its surface. This is thermionic emission. When a high potential is applied between the cathode and anode the emitted electrons are attracted towards the anode.

As the electrons accelerate in the field between the anode and cathode, they lose potential energy but gain K:E.

Gain in K:E = Loss in Electric P:E

1/2mv²=eV

m=mass of the electron,

v=velocity of the electron,

V=Potential between the plates,

e= charge of the electron.

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Deflecting electron beamsAn electron beam will follow a curved path when subjected to a perpendicular elecric field.

This is because the electron is subjected to a vertical force(F) due to the electric field.

F= eE=e V/d

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