please explain what is the exact mechanism of emission of photon by accelerated electron and the source of energy

The electron drops down an energy level emitting a photon and the difference in the energy level of the electron is in the photon

For accelerated electrons (or other charges) the process is called bremsstrahlung Acceleration causes the electric field to change, and changing E fields induce B fields and changing B fields induce E fields, which is EM radiation. The energy comes from the kinetic energy of the charged particle; the fact that the charge is accelerating means it is feeling a force, so there may also be work done on the charge, so the energy may ultimately be coming from that source (e.g. in an antenna)

Thank you for the information is the whole of kinetic energy of electron changed to photon energy:?

Thank you for the information is the whole of kinetic energy of electron changed to photon energy:?

 

I think it can be, in principle, but that requires it undergo no other interactions. In practice, that's hard to do.

Thank you for the information is the whole of kinetic energy of electron changed to photon energy:?

This must be possible in an atom, at a transition between two orbitals. Essentially all available energy, in this case electric energy reduced by kinetic energy, must convert into a photon.

 

Less easy for an unbound electron, since radiation is inefficient at low energy. But if the initial energy is highly relativistic and the electron looses nearly all of it in the collision with a nucleus, nearly all must convert into a photon.

 

In an X-ray tube, emitted photons can have about the energy of the incoming electrons, but most have less, because most collisions are not head-on.