Thermionic emission is the process where heated electrons are emitted from the surface of a cathode. When a potential is applied between the cathode and anode, the emitted electrons are attracted to the anode. As the electrons accelerate, they gain kinetic energy equal to the lost potential energy, following the equation that the gain in kinetic energy equals the loss in electric potential energy.

2. Electron beams
Q)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 1
field between the anode and
cathode, they lose potential energy 2
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.

4. Deflecting electron beams
An 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

5. Page 259.Example 4

6. Page.260 Example.5