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The electrons striking the anode get deflected by the heavy nucleus. Though the speed may or may not change, the direction of motion changes which leads to acceleration. The charged particles emit radiations when accelerated x-rays are produced.

So, why is it said that it is produced due to deceleration of electrons? Do the electrons surrounding the nucleus cause this deceleration? If so, which is the major reason for production of x-rays : (1) Deflection by the nucleus (2) Deceleration by surrounding electrons?

When I googled about x-ray production, different websites explained the production of x-rays in slightly different and I couldn't find the effects of repulsion by electrons surrounding the heavy nucleus of the anode in this process.

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  • $\begingroup$ There is no unique definition of acceleration vis a vis deceleration. The observer's frame of reference can change one into the other. $\endgroup$
    – dmckee --- ex-moderator kitten
    Commented Nov 27, 2014 at 15:55
  • $\begingroup$ @dmckee So, which has a major effect on deflecting the path of electrons, the attraction by nucleus or repulsion by electrons surrounding it? $\endgroup$
    – Rajath Radhakrishnan
    Commented Nov 29, 2014 at 13:03

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When a charged particle comes into the vicinity of another, it's path is deflected. It decelerates in one direction, and accelerates in another. All charged particles that are accelerated/decelerated by another charged particle, or a magnetic field, emit radiation.

See: Bremsstrahlung. Synchrotron radiation. Cyclotron radiation.

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The change in velocity of the electron give rise to emission of X-rays. The electrons arrive at the anode with very high velocity and end up at thermal velocities - which must mean they slowed down.

Both statements are therefore true.

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  • $\begingroup$ So, which has a major effect on deflecting the path of electrons, the attraction by nucleus or repulsion by electrons surrounding it? $\endgroup$
    – Rajath Radhakrishnan
    Commented Nov 28, 2014 at 15:54
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    $\begingroup$ Interesting question. While the interaction with the electrons is more important for changing the total momentum of the incoming electrons (because the electrons are light, more momentum is transferred to them), the greatest acceleration can be achieved by interaction with the nucleus (sling shot around it - nucleus remains "still"). I think. But there are more electrons than nuclei so I suspect (but have no hard data) that they are the more important particle. $\endgroup$
    – Floris
    Commented Nov 28, 2014 at 16:29
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The fast electrons slow down in the cathode, mostly due to interactions with atomic electrons. But hard X-rays are produced mostly due to deflection to large angles in the field of atomic nuclei. Roughly speaking, an atomic electron can stop the projectile electron in a head-on collision, but a nucleus can "reflect" the projectile back, so here the acceleration is stronger and the radiated quanta are harder. Of course, due to radiation, the "reflected" electron slows down a bit.

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