This presentation is all about X-Rays....

2. What are X-rays….
When high energetic electrons are made to
strike a metal target, an electromagnetic
radiation comes out a large part of this radiation
has wavelength of the order of 0.1mm(nearly
1A0) and is known as X-rays.
X-rays was discovered by German physicist
W.C.Roentgen in 1895.
He found that photographic film wrapped lighttight in a black paper near cathode ray tube.
He named these rays as x-rays.

3. X-rays
Frequencies: >3 x 1016 Hz.
Wavelengths: <10 nm.
Quantum energies: >124 eV.

4. Characteristics of X-rays
X-rays are not deflected by electric
and magnetic fields.
They are highly penetrating and can
pass through many solids. The
transparency depends on the density
of the material.
They effect a photographic plate and
even more effective than light.
They cause florescence in many
materials eg. Bariumplatinocyanide,

5. Continued from characteristics of X-rays…..
They have destructive effect on living
tissues. Exposure of human body to
X-rays causes reddening of the skin
and sores.
When X-rays fall on heavy metals,
they produce secondary x-rays.
Under suitable conditions X-rays are
reflected and refracted like ordinary
light.

6. Production of X-rays
Commonly used X-ray tube was
designed by Coolidge in 1916 and is
known as Coolidge tube.
It emits a large number of electrons
called thermions.
Velocity of these thermions depends
upon the potential difference between
cathode or anti cathode.
Cathode is surrounded by molybdenum
maintained at negative potential
difference between A and B.

7. Basic diagram of Coolidge
tube

8. Characteristics of an
anticathode
It should have high atomic weight.
High melting point to withstand high
temperature developed as most of
energy of impinging electrons
converted into heat.
High thermal conductivity.
Low vapour pressure at high
temperature.

9. Characteristics of
anticathode
Only tantalum, tungsten and
platinum.
But tungsten is the best and widely
used material.

10. Minimum wavelength of X-ray
photon
When the electron hitting the target is
brought to rest by the force of attraction
between this electron and the nucleus , the
entire K.E(.5mv2) is completely transformed
into X-ray photon of the maximum
frequency(Vmax)or minimum wavelength( λmin
)
ko = .5mv2=hVmax
Ko =hc/ λmin
λmin =hc/ko

11. Relation between potential difference
and wavelength:
Let V be the potential difference
between m cathode and anti-cathode
then,
Ko=.5mv2=eV
eV=hc/ λmin
λmin=hc /eV
Since h,c,e are the constants, therefore
λminœ 1/V


12. Types of X-rays on the basis of
energy
Hard X-rays
 Soft X-rays
Hard X-rays: X-rays of higher energy is
known as hard X-ray.
 If kinetic energy of the accelerating
electrons increased then cut off
wavelength will decrease further
resulting into production of X-rays of
lower wavelength which are known as
hard X-rays.


13. Soft X-rays
X-rays of longer wavelength are
known as soft X-rays.
 These have low energy.
 Soft X-rays have energies in the 0.09
to 2.5 keV range


14. Characteristic X-rays
Atom consist of nucleus surrounded
by negatively charged electrons.
Electrons in the innermost orbit is
attracted by nucleus strongly with
greatest force and large amount of
energy is required to detach it.
Electron in outermost orbit require
small amount of energy to detach it
from atom.

15. Continued from characteristic Xrays
When fast moving energetic electron
from cathode fall on anti cathode it will
penetrate deep into the surface of the
target and knock out tightly bound
electron from higher orbits jump to
occupy the position and difference in
the energy is radiated in the form of Xrays known as characteristic x-rays.

16. Continued from characteristic X-rays
Electrons make transitions
between lower atomic
energy levels in heavy
elements. They have definite
energies since they have
energies determined by the
atomic energy levels.

17. Continuous X-rays



When fast moving Energetic electron
penetrate deep into the interiors of the
atoms of the target and are attracted by
attractive forces of the nuclei.
Due to these forces electron may
deflect from the original paths and
electrons are retarded i.e. electron loose
its energy.
This loss in the energy is given in the
form of electromagnetic radiation known
as X-rays.

18. Diagram representing
characteristic and continuous Xray

19. Uses of the X-rays
Application in industry and
Engineering
1) X-rays are used to identify
manufacturing defects in tyres,
tennis balls and are also used to
check defects in diamond.
2) X-rays are used to check flaws in
welding joints, insulating material.
3) It can be used to analyze the
structure of alloys from diffraction


20. Medical Applications
X-rays for the diagnosis of many
diseases that cannot be identified by
pathological test.
It is used to find fractures in the
bones, diseased organs and presence
of foreign matter in the body.
X-rays can be used to cure many
types of skin diseases, malignant
sores,internal cancer and tumours.

21. Application in scientific
research
X-rays are used to study the structure
of the crystalline solids , atoms and
alloys.
X-rays diffraction pattern are used for
analyzing the structure of organic
complex molecules.
It can be used for the determination of
the atomic number of the element and
for identification of the chemical
elements.