X-rays
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1429-ﺷوال-27
Engineering Physics BS-124
By Atif M.Khokhar
1
Intro & History of X-rays Scientist Date
Nature of X-rays Bremsstrahlung process Characteristic X-rays The production of X-RAYS Properties of X-Rays Interaction with matter Application Space Exploration and X-Rays Atomic Spectra
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
1
2
1429-ﺷوال-27
Wilhelm Conrad Rontgen, German physicist, Who, on November 8, 1895, accidentally detected electromagnetic radiation, today known as x-rays or Roentgen rays.
An achievement that earned him the first Nobel Prize in Physics in 1901.
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
3
X Ray, penetrating electromagnetic radiation, having a shorter wavelength than light, and produced by bombarding a target, usually made of tungsten, with high-speed electrons
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
2
4
1429-ﺷوال-27
X rays are electromagnetic radiation ranging in wavelength from about 100 A to 0.01 A
10 um - 10 mm
700 to 104 nm 400 to 700 nm 10 to 400 nm 10-1 to 10 nm 10-4 to 10 -1 nm
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
Wave length range from 10 to 0.01nm
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
3
5
6
1429-ﺷوال-27
The shorter the wavelength of the X ray, the greater is its energy and its penetrating power.
Longer wavelengths, near the ultraviolet-ray band of the electromagnetic spectrum, are known as soft X rays.
The shorter wavelengths, closer to and overlapping the gamma-ray range, are called hard X rays Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
“ Process In which electromagnetic radiation produced by the acceleration of a charged particle (an electron), when deflected by another charged particle (an atomic nucleus). Electron radiates away from the site of encounter.” such radiations are called X-rays
Bremsstrahlung process (from the German bremsen, to brake and Strahlung, radiation, thus, "braking radiation" or "deceleration radiation"),
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
4
7
NOTE The phenomenon was discovered by Nikola Tesla during high frequency research he conducted between 1888 and 1897.
8
1429-ﺷوال-27
An incident electron penetrates the electron cloud of the atom and passes close to the nucleus.
The electron's kinetic energy is reduced as it is deflected from its original path. The energy lost by the electron takes the form
of
a
Bremsstrahlung
photon. Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
9
X-RAYS Continuous Spectrum
SPECTURM shifts toward higher frequencies when the energy of the bombarding electrons is increased Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
5
10
1429-ﺷوال-27
When a colliding electron excites an atom to highenergy state, that atom can then radiate an x-ray photon
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
11
M-orbital L-orbital Kb
K-absorption Ka1
Ka2
K-orbital
Wave-lengths Cu(Ka1)= 1.54015 Å; Cu(Ka2)= 1.54433 Å Cu(Ka)= 1.54015 Å Cu(Kb)= 1.39317 Å
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
6
12
1429-ﺷوال-27
7
The two sharp peaks in the illustration at left occur when vacancies are produced in the n=1 or K-shell of the atom and electrons drop down from above to fill the gap. The x-rays produced by are called K-alpha x-rays, and those for the n=2 transition are called K-beta x-rays. The continuous distribution of x-rays which forms the base for the two sharp peaks at left is called "Bremsstrahlung" radiation.
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
13
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
14
1429-ﺷوال-27
The target atoms consists of a small "block" of the target material, usually mounted on a heat removing substrate, and sometimes immersed in oil . The electrons come from a heated filament of ~10-50 mA current . The incident electrons acquire a high incident energy by being accelerated by the high voltage supply of tens of kV, connected across the target block and the filament. The resulting X-rays scatter away from the target, and pass through a window in the X-ray tube housing.
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
8
15
16
1429-ﺷوال-27
Accelerate electrons to 10kV - 100kV Let electrons hit heavy atoms Some x-rays emitted via Bremsstrahlung and some as characteristic X rays X-ray tube filters away lowest energy photons, which is good because they’re useless and burn
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
9
18
1429-ﺷوال-27
10
X rays affect a photographic emulsion in the same way light does . X rays also cause fluorescence in certain materials, such as barium platinocyanide and zinc sulfide. Another important characteristic of X rays is their ionizing power, which depends upon their wavelength. The capacity of monochromatic X rays to ionize is directly proportional to their energy. X rays may be diffracted by passage through a crystal or by reflection (scattering) from a crystal, which consists of regular lattices of atoms that serve as fine diffraction gratings. Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
19
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
20
1429-ﺷوال-27
In the interaction between matter and X rays, three mechanisms exist by which X rays are absorbed.
Photoelectric Effect Compton Scattering Pair Production
1. 2. 3.
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
When a photon, in the X-ray portion of the electromagnetic spectrum strikes an atom, it may intrude on an electron within an inner shell and eject it from the atom. If the photon carries more energy than is necessary to eject the electron, it will transfer its residual energy to the ejected electron in the form of kinetic energy. This phenomenon, called the photoelectric effect, occurs primarily in the absorption of low-energy X rays. Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
11
21
22
1429-ﺷوال-27
When a high-energy photon collides with an electron, both particles may be deflected at an angle to the direction of the path of the incident X ray. The incident photon, having delivered some of its energy to the electron, emerges with a longer wavelength. These deflections, accompanied by a change of wavelength, are known as Compton scattering.
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
When a high-energy photon penetrates the electron shell close to the nucleus, it may create a pair of electrons, one of negative charge and the other positive; a positively charged electron is also known as a positron. This pair production is an example of the conversion of energy into mass. The photon requires at least 1.2 MeV of energy to yield the mass of the pair. If the incident photon possesses more energy than is required for pair production, the excess energy is imparted to the electron pair as kinetic energy. The paths of the two particles are different.
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
12
23
24
1429-ﺷوال-27
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
When the square root of the frequencies of the characteristic x-rays from the elements is plotted against the atomic number, a straight line is obtained. In his early 20's, Moseley measured and plotted the x-ray frequencies for about 40 of the elements of the periodic table. He showed that the K-alpha x-rays followed a straight line when the atomic number Z versus the square root of frequency was plotted.
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
13
25
26
1429-ﺷوال-27
Used to detect Tuberculosis and disease of lungs Dentists used to check the condition of teeth before beginning the treatment. High energy X-rays are used to destroy cancer cells Used in CAT(computerized axial tomography)scan Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
X-rays are used to find the hidden flaws in the metals such as cracks, air holes strain in casting and imperfections in welds. Used to check the uniformity of the insulating materials. Use to distinguish between real and artificial diamond. Used for security purposes, like detection of Arms, explosives and precious metals
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
14
27
28
1429-ﺷوال-27
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
X-Ray Pictures
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
15
29
1429-ﺷوال-27
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
Caused by strong magnetic fields that may span up to 500,000 square kilometers
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
16
1429-ﺷوال-27
These occur anywhere on the Sun at opposition of the active regions. Caused by magnetic fields that are sucked down into the photosphere
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
Below: New Mexico’s Very Large Array
Above: Hawaii’s twin Keck observatories
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
17
1429-ﺷوال-27
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
18
1429-ﺷوال-27
Atomic Spectra
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
37
Atomic Spectra - Since the 19th century, it had been known that when elements are heated until they emit light (glow) they emit that light only at discrete frequencies, giving a line spectrum. -
+ Hydrogen Gas Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
19
Line Spectrum
1429-ﺷوال-27
Line spectra cannot be explained by the classical physics. We explain this phenomenon by utilizing two new concepts: 1. The particle nature of light (photons) 2. Energy levels: An atom can only have certain discrete energy values- we say that their energy is quantized. These energy values are called energy levels.
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
When an electron makes a transition from a higher energy level to a lower energy level ,the difference in the energy is emitted out as a photon . Each transition produces a photon of a certain energy and this appears as a line of certain wavelength on the spectrum. These lines constitute the Emission spectrum
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
20
1429-ﺷوال-27
When white light passes through a gas, the gas absorbs light of certain wavelengths that are not present in its emission spectrum. The resulting spectrum has some colors (wavelengths ) missing replaced by dark lines. This is called the Absorption spectrum.
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
21
1429-ﺷوال-27
Hydrogen spectrum
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
2/6/2008
43
Hydrogen Spectrum
Orbital diagram
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
22
44
Engineering Physics BS-124
By Atif M.Khokhar
1
Intro & History of X-rays Scientist Date
Nature of X-rays Bremsstrahlung process Characteristic X-rays The production of X-RAYS Properties of X-Rays Interaction with matter Application Space Exploration and X-Rays Atomic Spectra
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
1
2
1429-ﺷوال-27
Wilhelm Conrad Rontgen, German physicist, Who, on November 8, 1895, accidentally detected electromagnetic radiation, today known as x-rays or Roentgen rays.
An achievement that earned him the first Nobel Prize in Physics in 1901.
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
3
X Ray, penetrating electromagnetic radiation, having a shorter wavelength than light, and produced by bombarding a target, usually made of tungsten, with high-speed electrons
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
2
4
1429-ﺷوال-27
X rays are electromagnetic radiation ranging in wavelength from about 100 A to 0.01 A
10 um - 10 mm
700 to 104 nm 400 to 700 nm 10 to 400 nm 10-1 to 10 nm 10-4 to 10 -1 nm
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
Wave length range from 10 to 0.01nm
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
3
5
6
1429-ﺷوال-27
The shorter the wavelength of the X ray, the greater is its energy and its penetrating power.
Longer wavelengths, near the ultraviolet-ray band of the electromagnetic spectrum, are known as soft X rays.
The shorter wavelengths, closer to and overlapping the gamma-ray range, are called hard X rays Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
“ Process In which electromagnetic radiation produced by the acceleration of a charged particle (an electron), when deflected by another charged particle (an atomic nucleus). Electron radiates away from the site of encounter.” such radiations are called X-rays
Bremsstrahlung process (from the German bremsen, to brake and Strahlung, radiation, thus, "braking radiation" or "deceleration radiation"),
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
4
7
NOTE The phenomenon was discovered by Nikola Tesla during high frequency research he conducted between 1888 and 1897.
8
1429-ﺷوال-27
An incident electron penetrates the electron cloud of the atom and passes close to the nucleus.
The electron's kinetic energy is reduced as it is deflected from its original path. The energy lost by the electron takes the form
of
a
Bremsstrahlung
photon. Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
9
X-RAYS Continuous Spectrum
SPECTURM shifts toward higher frequencies when the energy of the bombarding electrons is increased Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
5
10
1429-ﺷوال-27
When a colliding electron excites an atom to highenergy state, that atom can then radiate an x-ray photon
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
11
M-orbital L-orbital Kb
K-absorption Ka1
Ka2
K-orbital
Wave-lengths Cu(Ka1)= 1.54015 Å; Cu(Ka2)= 1.54433 Å Cu(Ka)= 1.54015 Å Cu(Kb)= 1.39317 Å
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
6
12
1429-ﺷوال-27
7
The two sharp peaks in the illustration at left occur when vacancies are produced in the n=1 or K-shell of the atom and electrons drop down from above to fill the gap. The x-rays produced by are called K-alpha x-rays, and those for the n=2 transition are called K-beta x-rays. The continuous distribution of x-rays which forms the base for the two sharp peaks at left is called "Bremsstrahlung" radiation.
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
13
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
14
1429-ﺷوال-27
The target atoms consists of a small "block" of the target material, usually mounted on a heat removing substrate, and sometimes immersed in oil . The electrons come from a heated filament of ~10-50 mA current . The incident electrons acquire a high incident energy by being accelerated by the high voltage supply of tens of kV, connected across the target block and the filament. The resulting X-rays scatter away from the target, and pass through a window in the X-ray tube housing.
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
8
15
16
1429-ﺷوال-27
Accelerate electrons to 10kV - 100kV Let electrons hit heavy atoms Some x-rays emitted via Bremsstrahlung and some as characteristic X rays X-ray tube filters away lowest energy photons, which is good because they’re useless and burn
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
9
18
1429-ﺷوال-27
10
X rays affect a photographic emulsion in the same way light does . X rays also cause fluorescence in certain materials, such as barium platinocyanide and zinc sulfide. Another important characteristic of X rays is their ionizing power, which depends upon their wavelength. The capacity of monochromatic X rays to ionize is directly proportional to their energy. X rays may be diffracted by passage through a crystal or by reflection (scattering) from a crystal, which consists of regular lattices of atoms that serve as fine diffraction gratings. Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
19
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
20
1429-ﺷوال-27
In the interaction between matter and X rays, three mechanisms exist by which X rays are absorbed.
Photoelectric Effect Compton Scattering Pair Production
1. 2. 3.
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
When a photon, in the X-ray portion of the electromagnetic spectrum strikes an atom, it may intrude on an electron within an inner shell and eject it from the atom. If the photon carries more energy than is necessary to eject the electron, it will transfer its residual energy to the ejected electron in the form of kinetic energy. This phenomenon, called the photoelectric effect, occurs primarily in the absorption of low-energy X rays. Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
11
21
22
1429-ﺷوال-27
When a high-energy photon collides with an electron, both particles may be deflected at an angle to the direction of the path of the incident X ray. The incident photon, having delivered some of its energy to the electron, emerges with a longer wavelength. These deflections, accompanied by a change of wavelength, are known as Compton scattering.
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
When a high-energy photon penetrates the electron shell close to the nucleus, it may create a pair of electrons, one of negative charge and the other positive; a positively charged electron is also known as a positron. This pair production is an example of the conversion of energy into mass. The photon requires at least 1.2 MeV of energy to yield the mass of the pair. If the incident photon possesses more energy than is required for pair production, the excess energy is imparted to the electron pair as kinetic energy. The paths of the two particles are different.
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
12
23
24
1429-ﺷوال-27
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
When the square root of the frequencies of the characteristic x-rays from the elements is plotted against the atomic number, a straight line is obtained. In his early 20's, Moseley measured and plotted the x-ray frequencies for about 40 of the elements of the periodic table. He showed that the K-alpha x-rays followed a straight line when the atomic number Z versus the square root of frequency was plotted.
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
13
25
26
1429-ﺷوال-27
Used to detect Tuberculosis and disease of lungs Dentists used to check the condition of teeth before beginning the treatment. High energy X-rays are used to destroy cancer cells Used in CAT(computerized axial tomography)scan Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
X-rays are used to find the hidden flaws in the metals such as cracks, air holes strain in casting and imperfections in welds. Used to check the uniformity of the insulating materials. Use to distinguish between real and artificial diamond. Used for security purposes, like detection of Arms, explosives and precious metals
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
14
27
28
1429-ﺷوال-27
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
X-Ray Pictures
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
15
29
1429-ﺷوال-27
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
Caused by strong magnetic fields that may span up to 500,000 square kilometers
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
16
1429-ﺷوال-27
These occur anywhere on the Sun at opposition of the active regions. Caused by magnetic fields that are sucked down into the photosphere
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
Below: New Mexico’s Very Large Array
Above: Hawaii’s twin Keck observatories
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
17
1429-ﺷوال-27
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
18
1429-ﺷوال-27
Atomic Spectra
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
37
Atomic Spectra - Since the 19th century, it had been known that when elements are heated until they emit light (glow) they emit that light only at discrete frequencies, giving a line spectrum. -
+ Hydrogen Gas Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
19
Line Spectrum
1429-ﺷوال-27
Line spectra cannot be explained by the classical physics. We explain this phenomenon by utilizing two new concepts: 1. The particle nature of light (photons) 2. Energy levels: An atom can only have certain discrete energy values- we say that their energy is quantized. These energy values are called energy levels.
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
When an electron makes a transition from a higher energy level to a lower energy level ,the difference in the energy is emitted out as a photon . Each transition produces a photon of a certain energy and this appears as a line of certain wavelength on the spectrum. These lines constitute the Emission spectrum
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
20
1429-ﺷوال-27
When white light passes through a gas, the gas absorbs light of certain wavelengths that are not present in its emission spectrum. The resulting spectrum has some colors (wavelengths ) missing replaced by dark lines. This is called the Absorption spectrum.
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
21
1429-ﺷوال-27
Hydrogen spectrum
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
2/6/2008
43
Hydrogen Spectrum
Orbital diagram
Lecture delivered @ HITEC UNIVERSITY, Taxila, by Atif M. Khokhar
22
44
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