this how X-ray is being created...!!?

1. Production of X-rays
Where do x-rays come from?
An x-ray machine, like that
used in a doctor's or a
dentist's office, is really
very simple. Inside the machine
is an x-ray tube. An electron gun
inside the tube shoots high
energy electrons at a target made
of heavy atoms, such as
tungsten. X-rays come out
because of atomic processes
induced by the energetic
electrons shot at the target.
X-rays are just like any other kind of
electromagnetic radiation. They can be produced in
parcels of energy called photons, just like light.
There are two different atomic processes that can
produce x-ray photons. One is called Bremsstrahlung,
which is a fancy German name meaning "braking
radiation." The other is called K-shell emission. They can
both occur in heavy atoms like tungsten.
So do both ways of making x-rays involve a change
in the state of electrons?

2. That's right. But Bremsstrahlung is easier to
understand using the classical idea that radiation is
emitted when the velocity of the electron shot at the
tungsten changes. This electron slows down after
swinging around the nucleus of a tungsten atom and loses
energy by radiating x-rays. In the quantum picture, a lot of
photons of different wavelengths are produced, but none of
the photons has more energy than the electron had to begin
with. After emitting the spectrum of x-ray radiation the
original electron is slowed down or stopped.
What is the "K-shell" in the other way of making x-
rays?
Do you remember that atoms have their electrons
arranged in closed "shells" of different
energies? Well, the K-shell is the lowest
energy state of an atom.
What can the incoming electron from the electron
gun do to a K-shell electron in a tungsten target
atom?
It can give it enough energy to knock it out of its
energy state. Then, a tungsten electron of higher
energy (from an outer shell) can fall into the K-shell.
The energy lost by the falling electron shows up in an
emitted x-ray photon. Meanwhile, higher energy electrons
fall into the vacated energy state in the outer shell, and so

3. on. K-shell emission produces higher-intensity x-rays than
Bremsstrahlung, and the x-ray photon comes out at a single
wavelength. Have a look at both mechanisms in the
experiment below.
Bremsstrahlung
Why is tungsten used in x-ray tubes? Can't other
elements produce x-rays?
Most elements emit x-rays when properly
bombarded with electrons. Heavier elements (like
tungsten) are best because they emit a higher
intensity through bremsstrahlung, but there are
plenty of heavy elements to choose from. The real issue is
engineering: Most electrons that hit the tungsten don't do
anything special at all -- no bremsstrahlung, no K-shell
emission. All of the energy from the electrons' impact then
goes into heating the tungsten. Tungsten is used because it
can withstand this bombardment, as it has a high melting
point and can conduct heat away very well.
What would happen if you replaced the tungsten
with something else?
The bremsstrahlung pattern looks very similar no
matter what element you use. The K-shell emission
spectrum is unique and different for each
element.

4. In bremsstrahlung, why is a range of photons emitted
instead of just one wavelength?
The incoming electron is accelerated and strikes the
tungsten at a high speed and has a lot of energy.
Recall that we called it "braking radiation." The
electron might be slowed a little or a lot.
So the amount of "braking"
determines which
wavelength of photons are
emitted.
Yes, but there is more. If we represent all of the
energy of the electron as a pie, there are bazillions
of different ways of cutting up this pie.

5. But one thing's for sure, you can
never end up with more pie than
you started with. If all of the
energy goes into producing only
one photon, there is no way you could
have a photon with more energy than
that!
So there should be a sharp cut-off in the
spectrum. It looked like there was a cut-
off on each end.
No, there is only one cut-off that corresponds to a
minimum wavelength. There is no limit to a
maximum wavelength emitted. Go back to the
bremsstrahlung spectrum and see how it fades
gradually to zero for long wavelengths.
K-Shell Emission
In the K-shell process, what's with that electron that
drifts in from nowhere after the electron gets
knocked-out?

6. A heavy atom has lots of electrons surrounding the
nucleus in various shells. To keep it simple I didn't
show them all. Really that electron that drifts in
comes from one of the other shells of the atom. The
K-shell knock-out affects the innermost electron, so its like
having a hole in the bottom. This "hole" causes a domino
effect where the electrons above it cascade down to fill the
hole.
But why the innermost electron? I would have guessed
the outermost electron would be the easiest to knock
out.
An x-ray photon has a lot of energy in it, and only
transitions of the inner electrons release that much
energy. Transitions of the outer electrons, which can
happen, might be in the infrared or visible part of the
spectrum. For the electron energies used in x-ray tubes, it
turns out the inner electrons are the most likely to be
knocked out.
You said earlier that the K-shell spectrum depends on
the target element. Why?
Remember that we said each
elements has its team colors? We're
looking at the transition between two
states, so we are looking at the team
colors in the x-ray part of the spectrum.

7. These fingerprints were used by Moseley to
help understand atoms with lots of electrons.
What did Moseley actually do?
Back in 1913 when he was a graduate student
he looked at the K-shell radiation coming out
from various elements from aluminum to gold. He
found a connection between the wavelength of the
emitted K-shell x-ray and the element (atomic number) that
helped us understand atoms better.
How can you find the wavelength of an x-ray?
That seems like a hard thing to measure.
That's another story in itself. He used the (then)
recently developed technique called Bragg scattering,
where you scatter x-rays off a crystal. He was able
to predict the existence of elements not yet
observed, such as technetium, promethium and rhenium.
And even today, because of the uniqueness of the
fingerprints of each element, x-rays are used for chemical
analysis as it is very sensitive to impurities.