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INAYA MEDICAL COLLEGE (IMC)
RAD 232 - LECTURE 1
RADIATION PHYSICS
DR. MOHAMMED MOSTAFA EMAM
Radiation:
It is defined as the process by which
energy is emitted from a source and
propagated through the surrounding
medium.
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NUCLEUS CHARACTERISTICS
• This appear is a nucleus; the red ones are
going to be the protons and the blue ones are
going to be the neutrons.
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NUCLEUS CHARACTERISTICS
• If we look at the periodic table, we can see
neon has same number of proton and
neutron, similar way calcium also has same
no. of neutrons and protons.
Stable atoms
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NUCLEUS CHARACTERISTICS
• Uranium have 92P and 146N.
Why is that???
Nucleus is held together by a strong
nuclear force; All these nucleons are held
together by this force (came from
neutrons) which hold the nucleus
together.
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Radioactivity : It is the act of emitting radiation
spontaneously from the unstable atoms.
 Unstable atoms differ from stable atoms
because they have an excess of energy or
mass or both.
 Unstable atoms are known as radioactive
atoms.
E.g. Carbon 14, Uranium 238
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CLASSIFICATION OF RADIATION
Radiation
Non-ionizing
Ionizing
Directly ionizing;
(charged particles)
electrons, protons, etc
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Indirectly ionizing
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NON-IONIZING RADIATION
 Non-ionizing radiation refers to any type of
electromagnetic radiation that does not carry
enough energy to ionize an atom or molecule.
Examples:
Near ultraviolet radiation
infrared radiation,
microwave,
radio waves, etc
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IONIZING RADIATION
 Ionizing radiation has sufficient energy to ionize an
atom or molecule.
 Ionization is a process in which a charged portion
of a molecule (usually electron) is given enough
energy to break away from the atom.
 Ionization results in the formation of charged
particles or ions; the molecule with net positive
charge and the free electron with a net negative
charge.
 All ionizing radiation is capable, directly and
indirectly of removing electrons from most of the
molecules.
 Ionizing radiation has enough energy to damage
DNA in cells which in turn may lead to cancer.
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ALPHA RADIATION
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Characteristics of alpha radiation:
 Alpha radiation is not able to penetrate skin.
 Alpha emitting materials can be harmful to
humans if the materials are inhaled, swallowed
or absorbed through open wounds.
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Characteristics of alpha radiation:
 Alpha radiation is not able to penetrate skin.
Alpha radiation is the least penetrating.
It can be stopped (or absorbed) by a sheet of paper.
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Characteristics of alpha radiation:
When alpha particles are emitted outside our bodies,
virtually all of their ionizing radiation is harmlessly
absorbed by the nonliving outer layer of our skin.
This means that alpha radiation doesn’t have much
effect on our health unless radioactive isotopes get
inside our bodies and emit radiation internally .
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 Alpha radiation travels a very short distance
through air.
 A variety of instruments have been
designed to measure alpha radiation.
Instruments can not detect alpha radiation
even a thin layer of water, blood, dust, paper
or other material, because alpha radiation is
not penetrating
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USES OF ALPHA RADIATIONS
 Alpha particles are most commonly used in
smoke alarms (smoke detectors). The alpha
particles ionize air between a
small gap. A small current is
pass through the ionized air.
Smoke particles from fire that
enter the air gap reduces the current flow,
sounding the alarm.
 Alpha decay can produce safe power sources
for radioisotope thermoelectric generators
used for space probes and artificial heart
pacemakers.
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BETA RADIATION
 Beta radiation is a stream of electrons called beta
particles. When a beta particle is ejected, a neutron
in the nucleus is converted to a proton, so the mass
number of nucleus is unchanged, but the atomic
number increases by one unit.
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Thorium undergoes radioactive decay to
form Protactinium and beta particle.
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Characteristics of beta radiation:
 Beta radiation is more hazardous because it can
also cause ionization of living cells. If the particles
hits a molecule of DNA it can cause spontaneous
mutation and cancer.
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Characteristics of beta radiation:
 Beta emitting contaminants may be harmful if deposited
internally.
 Beta radiation may travel meters in air and is moderately
penetrating, so It can penetrate human skin to “germinal
layer” where new cells are produced.
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Characteristics of beta radiation:
 Beta radiation is more hazardous because it can
also cause ionization of living cells. If the particles
hits a molecule of DNA it can cause spontaneous
mutation and cancer.
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Characteristics of beta radiation:
 Beta radiation is more hazardous because it can
also cause ionization of living cells. If the particles
hits a molecule of DNA it can cause spontaneous
mutation and cancer.
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 Beta radiation cannot be detected with an ionization
chamber such as a CD V-715.
 Clothing and turnout gear provide some protection
against most beta radiation. Turnout gear and dry
clothing can keep beta emitters off of the skin.
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USES OF BETA RADIATIONS
 Beta radiation are widely used in medicine. In
brachytherapy, beta radioisotopes can be used to
irradiate areas inside a patient to prevent the growth
of certain tissues.
 Beta particles are also used in some forms of
therapy to kill cancer cells.
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USES OF BETA RADIATIONS
• Brachytherapy is a procedure that involves
placing radioactive material inside your body.
• Brachytherapy is one type of radiation
therapy that's used to treat cancer.
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USES OF BETA RADIATIONS
• Brachytherapy is sometimes called internal
radiation.
• Brachytherapy allows doctors to deliver
higher doses of radiation to more-specific
areas of the body, compared with the
conventional form of radiation therapy
(external beam radiation) that projects
radiation from a machine outside of your
body.
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USES OF BETA RADIATIONS
• Brachytherapy may cause fewer side effects
than does external beam radiation, and the
overall treatment time is usually shorter with
brachytherapy.
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USES OF BETA RADIATIONS
 Beta radiation is used in leak detection
in the pipeline. This is achieved by
adding small amount of beta radiation
to the fluid.
The area above the ground where high
intensity of beta radiation is detected
will pin point the leak sources in the
pipeline.
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USES OF BETA RADIATIONS
• Carbon-14 is used as tracers in
chemical and biological research.
• The age of the ancient organic
materials can also be found by
measuring the amount of Carbon-14
that is left.
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GAMMA RADIATION
 Gamma radiation is electromagnetic radiation of
high frequency and therefore high photons with a
very short wavelength.
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GAMMA RADIATION
 The emission of gamma radiation results from an
energy change within the atomic nucleus.
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GAMMA RADIATION
• It should be noted that the emission of gamma rays
does not change the mass number or atomic
number of the nucleus.
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GAMMA RADIATION
• Alpha and beta emission are often accompanied by
gamma emission, as an excited nucleus drops to a
lower and more stable energy change.
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X-RAYS
 X-ray photons carry enough energy to ionize atoms
and disrupt molecular bond.
 This makes it a type of ionizing radiation and
thereby harmful to living tissues.
 X-ray machine sends individual x-ray particles
through the body. The image is recorded on a
computer or film.
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Characteristics of gamma radiation and x-rays:
 Gamma radiation and X-rays are electromagnetic
radiation like visible light, radio waves, and
ultraviolet light. These electromagnetic radiations
differ only in the amount of energy they have.
Gamma rays and X-rays are the most energetic of
these.
 X-rays are like gamma rays. They, too, are
penetrating radiation.
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 Gamma radiation is able to travel many meters in air
and many centimeters in human tissue.
 Radioactive materials that emit gamma radiation and
X-rays constitute both an external and internal hazard to
humans
 Gamma radiation or X-rays frequently accompany the
emission of alpha and beta radiation
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 Gamma radiation is detected with survey
instruments, including civil defense instruments.
Low levels can be measured with a standard Geiger
counter, such as the CD V-700. High levels can be
measured with an ionization chamber, such as a CD
V-715.
 Instruments designed solely for alpha detection will
not detect gamma radiation
 Pocket chamber (pencil) dosimeters, film badges,
thermo luminescent, and other types of dosimeters
can be used to measure accumulated exposure to
gamma radiation.
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USES OF GAMMA RADIATIONS
 Even after it has been packaged, gamma rays can
be used to kill bacteria, mould and insects in food.
This process prolongs the shelf-life of the food, but
sometimes changes the taste.
 Gamma rays are also used to sterilise hospital
equipment, especially plastic syringes that would be
damaged if heated.
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 The most common tracer is called Technetium-99 and is
very safe because it only emits gamma rays and doesn't
cause much ionization.
• Radioisotopes can be used for medical purposes, such
as checking for a blocked kidney.
To do this a small amount of Iodine-123 is injected into
the patient, after 5 minutes 2 Geiger counters are placed
over the kidneys.
• Also radioisotopes are used in industry, to detect leaking
pipes. To do this, a small amount is injected into the pipe.
It is then detected with a GM counter above ground.
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 Checking welds. If a gamma source is placed on
one side of the welded metal, and a photographic
film on the other side, weak points or air bubbles will
show up on the film, like an X-ray.
 Because Gamma rays can kill living cells, they are
used to kill cancer cells without having to resort to
difficult surgery. This is called "Radiotherapy", and
works because cancer cells can't repair themselves
when damaged by gamma rays, as healthy cells can
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USES OF X-RAYS
 X-rays are used in medicine for medical analysis.
Dentists use them to find complications, cavities and
impacted teeth. Soft body tissue are transparent to
the waves. Bones also block the rays.
 X-rays are used in industry to inspect
products made by various kinds of
materials. X-ray machines are used
in airports to check luggage etc.
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 In Science x-rays are used to analyze the
arrangement of atoms in many kinds of substances,
particularly crystals. Archaeologists used X-rays to
examine ancient objects covered by a crust of dirt.
 X-rays are also used in consumer goods the
manufactures treat certain kinds of plastic to check
the quality of many mass produced products.
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