laser & X-ray production presentation

1. GROUP#3
Applied Physics
Laser & X-Rays
GROUP MEMBERS:
1-Hafeez Rasheed
2-M.Husnain
3.Saqlain Abbas
4-Attiq-ur-Rehman
5-Farhad Iqbal

2. LASER
History and Introduction
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• The first laser was built in 1960 by Theodore H. Maiman at Hughes
Research Laboratories, based on theoretical work by Charles Hard
Townes and Arthur Leonard Schawlow.
• “Laser” is an acronym for “Light Amplification by Stimulated Emission of
Radiation”
• A laser is a device that emits light through a process of optical
amplification based on the stimulated emission of electromagnetic
radiation.

3. LASER
History and Introduction
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• LASER is an invention of the twentieth century. The operating principle of
many types of lasers depend directly on the quantum mechanical
structure of the atom.
• It has already been shown that a photon is emitted when an electron
makes a transition from a higher energy state to a lower energy state.
• This is called spontaneous emission
• Normally in spontaneous emission, an electron in an atom eventually
drops to a lower level in a time that is about 10*8 sec giving off a photon
in this process
• The operation of a laser depends on stimulated emission,
• An incoming photon stimulates an electron to change energy levels.

4. Design of a LASER
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• A laser consists of a gain medium, a mechanism to energize it, and
something to provide optical feedback.
• The gain medium is a material with properties that allow it
to amplify light by way of stimulated emission.
• Light of a specific wavelength that passes through the gain medium is
amplified (increases in power).
• For the gain medium to amplify light, it needs to be supplied with energy
in a process called pumping.
• The energy is typically supplied as an electric current or as light at a
different wavelength. Pump light may be provided by a flash lamp or by
another laser.

5. Design of a LASER
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• The most common type of laser uses feedback from an optical cavity—a
pair of mirrors on either end of the gain medium.
• Light bounces back and forth between the mirrors, passing through the
gain medium and being amplified each time.
• Typically one of the two mirrors, the output coupler, is partially
transparent.
• Some of the light escapes through this mirror. Depending on the design
of the cavity (whether the mirrors are flat or curved), the light coming
out of the laser may spread out or form a narrow beam.
• In analogy to electronic oscillators, this device is sometimes called
a laser oscillator.

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7. LASER
History and Introduction
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• LASER is an invention of the twentieth century. The operating principle of
many types of lasers depend directly on the quantum mechanical
structure of the atom.
• It has already been shown that a photon is emitted when an electron
makes a transition from a higher energy state to a lower energy state.
• This is called spontaneous emission
• Normally in spontaneous emission, an electron in an atom eventually
drops to a lower level in a time that is about 10*8 sec giving off a photon
in this process
• The operation of a laser depends on stimulated emission,
• An incoming photon stimulates an electron to change energy levels.

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Properties of LASER
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These three properties of laser light are what make it more of a hazard
than ordinary light.
Monochromatic
Directional
Coherent
Many different types of lasers have been developed, with highly
varied characteristics

9. Monochromatic
 T h e l i g h t e m i t t e d f r o m a l a s e r
i s m o n o c h r o m a t i c , t h a t i s , i t i s o f o n e
w a v e l e n g t h ( c o l o r ) .
 I n c o n t ra s t , o r d i n a r y w h i t e l i g h t i s a
c o m b i n a t i o n o f m a ny d i f fe re n t w a v e l e n g t h s
( c o l o r s ) .

10. Directional
 Lasers emit lig ht th at is h ig h ly directio nal.
 Laser lig ht is emitted as a relatively
n arrow b eam in a sp ec ific d irec tion .
 O rd in ar y lig ht, su ch as comin g from th e
su n , a lig ht b u lb , or a can d le, is emitted in
many d irec tion s away from th e sou rc e.

11. Coherent
 Th e lig ht from a laser is said to
b e coh erent , wh ic h mean s th e wavelen gth s
of th e laser lig ht are in p h ase in sp ac e an d
time.

12. Types of LASER
 S o l i d - s t a t e l a s e r
 G a s l a s e r
 L i q u i d l a s e r
 S e m i c o n d u c t o r l a s e r

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LASER Elements
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 Population inversions can be produced in a gas, liquid, or solid, but most laser media are gases or solids.
 Typically, laser gases are contained in cylindrical tubes and excited by an electric current or external light
source, which is said to “pump” the laser.
 Similarly, solid-state lasers may use semiconductors or transparent crystals with small concentrations of
light-emitting atoms.

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Applications of LASER
The most significant applications of lasers include:
 Lasers in medicine
 Lasers in communications
 Lasers in industries
 Lasers in science and technology
 Lasers in military

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LASER in Medicine
 Bloodless surgery
 Destroy kidney stones
 Cancer diagnostics and surgery
 Eye lens curvature correction
 Creation of PLASMA
 Treatment of Liver and Lung diseases
 Removal of tumors
 Removal of Caries
 Cosmetic treatments e.g. acne treatment and cellulite

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LASER in Communication
 Laser light is used in optical fiber
communications to send information over
large distances with low loss.
 Laser light is used in underwater
communication networks.
 Lasers are used in space communication,
radars and satellites

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LASER in Industries
 To cut glass and quartz
 In electronic industries
 Heat treatment
 To drill aerosol nozzles and control orifices

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LASER in Science
 Study of Brownian motion of particles
 Counting of number of atoms
 Store data on CD-ROM
 To retrieve information from CD (Compact Disc)
 Determination of rate of rotation of earth
 Used in computer printers
 To setup invisible fence to protect an area

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LASER in Military
 Used in LIDAR’s to accurately measure the distance to an object.
 The ring laser gyroscope is used for sensing and measuring very small angle of rotation of the moving objects.
 Lasers are used to dispose the energy of a warhead by damaging the missile.

20. X-RAYS

21. X-RAYS
History and Introduction
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• Wilhelm Conrad Roentgen
• German Physicist
• A professor at Wurzburg University in Germany
• Discovered X-rays (Nov-8 , 1895)
• 1st noble prize in Physics in 1901

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What are X-Rays
Most X-rays have a wavelength ranging from 0.01 to 10 nanometers, corresponding to frequencies in the range 30 pet
hertz to 30 exahertz (3×1016 Hz to 3×1019 Hz) and energies in the range 100 eV to 100 keV.
X-ray wavelengths are shorter than those of UV rays and typically longer than those of gamma rays.
In many languages, X-radiation is referred to as Rontgen radiation

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How X-Rays were produced
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 Roentgen noticed crystals near a high-voltage cathode-ray tube exhibiting a fluorescent glow, even when he
shielded them with dark paper.
 Some form of energy was being produced by the tube that was penetrating the paper and causing the crystals to
glow. Roentgen called the unknown energy "X-radiation.“
 Experiments showed that this radiation could penetrate soft tissues but not bone, and would produce shadow
images on photographic plates.
 For this discovery, Roentgen was awarded the very first Nobel Prize in physics, in 1901.

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First Experiment
 He first experimented by placing his wife’s hands on photographic fluorescent plate for 15
minutes
 When he developed the plate, the outline of the bones of her hand could be seen
 He named these Unknown rays as X-radiations

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Production of X-Rays
An important source of X rays is synchrotron radiation . X rays are also produced in a highly evacuated glass bulb, called
an X-ray tube, that contains essentially two electrodes—an anode made of platinum, tungsten, or another heavy metal
of high melting point, and a cathode. When a high voltage is applied between the electrodes, streams of electrons
(cathode rays) are accelerated from the cathode to the anode and produce X rays as they strike the anode.
Two different processes give rise to radiation of X-ray frequency.
1. In one process radiation is emitted by the high-speed electrons themselves as they are slowed or even stopped in
passing near the positively charged nuclei of the anode material.
2. In a second process radiation is emitted by the electrons of the anode atoms when incoming electrons from the
cathode knock electrons near the nuclei out of orbit and they are replaced by other electrons from outer orbits.
The spectrum of frequencies given off with any particular anode material thus consists of a continuous range of
frequencies emitted in the first process, and superimposed on it a number of sharp peaks of intensity corresponding
to discrete frequencies at which X rays are emitted in the second process.

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Modern X-Rays working
 X-rays were found to be able to penetrate through materials of light atoms like flesh. Havier atoms like metal absorb
them.
 A beam of high energy electrons crashes into a metal target and X-rays are produced. A filter near the X-Ray source
blocks the low energy rays so only the high energy rays pass through a patient towards a sheet of film.
 Along with the sheet of film ,a second sheet of film prevents the scattered x-rays from fogging the picture.
 Calcium in bones is considered a type of metal and when photographic film is placed on the body ,it allows the
technician to take the picture and X-ray is developed to solve or analyze the problem
 The soft tissue in a human body is composed of smaller atoms, and so does not absorb X-ray photons particularly as
well.
 The calcium atoms that make up your bones are much larger, so they are better at Absorbing X-ray’s photons

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Applications and Uses
• Broken Bones
Today, x-rays are an integral part of contemporary hospitals and medical centers. This is their
most common application, with doctor’s using machines to take photographs of a patient’s body.
Photographic film is placed behind the body, with the x-ray then turned on. The rays easily pass
through the skin, but take a little longer to travel through the bone. This is why bones appear much
lighter in color. Using the results, doctors can develop effective treatment plans

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• Radiation Therapy
 X-rays play an important role in the fight against cancer, with high energy radiation used to kill
cancer cells and shrink tumors.
 Patients undergo treatment outside the body (known as external-beam radiation therapy) or from
radioactive material that’s inserted into the body in close proximity to cancer cells. This is called
internal radiation therapy, or brachytherapy.
Radiation therapy can be dangerous, yet it’s still received by around 50% of cancer patients during
the course of their treatment.

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• Airport Security
 Almost every airport on the planet is now fitted with some form of x-ray security
system that scans baggage to check for dangerous items.
 In the past few years full body x-ray scans have also emerged as an additional
security measure.

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• Revealing Counterfeit Art
Perhaps one of the lesser known uses, x-rays are also used by art historians to
detect whether or not a picture has been painted over an existing piece.

35. Thank You.