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Radiation physics
1. RADIATION
PHYSICS
Presented by: Fathimath Shibana
Msc. Biotechnology
First semester 2012
University of Mysore
Guided by: Dr. H.S. Aparna
Associate professor
DOS in Biotechnolog
2. Radiation :
It is defined as the process by which
energy is emitted from a source and
propagated through the surrounding
medium.
4. 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
7. 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.
Near ultraviolet radiation
infrared radiation,
microwave,
radio waves, etc
8. 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.
12. 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.
13. 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
14. 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.
15. 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.
16.
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.
Characteristics of beta radiation:
Beta radiation may travel meters in air and is moderately
penetrating.
It can penetrate human skin
to “germinal layer” where new
cells are produced.
17. Beta emitting contaminants may be harmful if deposited
internally
Most beta emitters can be detected with survey
instruments. (e.g. CD-V-700). Some beta emitters,
however produce very low energy, poorly penetrating
radiation that may be difficult or impossible to detect.
Examples of these are carbon-14,
tritium, and sulfur-35.
18.
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.
19. USES OF BETA RADIATIONS
Beta radiation are widely used in medicine. In branchy
therapy, 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.
Beta particles are used in quality control to test the
thickness of an item, such as paper,
coming through a
system of
rollers.
20. 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.
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.
21. GAMMA RADIATION
Gamma radiation is electromagnetic radiation of high
frequency and therefore high photons with a very short
wavelength.
The emission of gamma radiation results from an
energy change within the atomic nucleus.
Gamma radiation change neither the atomic number
nor the atomic mass.
Alpha and beta emission are often accompanied by
gamma emission, as an excited nucleus drops to a lower
and more stable energy change.
22.
23. 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.
24. 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.
25.
Gamma radiation is able to travel many meters in air and
many centimeters in human tissue.
Radioactive materials that emit gamma radiation and Xrays constitute both an external and internal hazard to
humans
Gamma radiation or X-rays frequently accompany the
emission of alpha and beta radiation
26. 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.
27. 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.
28. 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.
29. 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
30. 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.
31.
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.
Radiation is the energy that is given off by the radioactive atom. Eg. Carbon 14, Uranium 238, etc
How does radiation work. To understand this you need to understand fundamental forces.
This appear is a nucleus. The red ones are going to be the protons and the blue ones are going to be the neutrons. If we look at the periodic table, we can see neon have same number of proton and neutro, similar way calcium also have same no. of neutrons and protons. Sn (tin) have 50 P and 70 N. so here number of proton is less compare to the number of neutrons. Uranium have 92P and 146N. Why is that??? The reason is nucleus is held together by a strong nuclear force. All these nucleons are held together by this force which hold the nucleus together. Nucleus loves to shed apart. The reason is it has positive charges, when number of it is small there will be a strong nuclear forces to hold it together. In U, it has 146N to hold the 92P.
Why they emit radiation spontaneously?? It is because the unstable atomic radius wants to give some energy in order to shift to more stabel configuration.
Radiation is classified into two groups. Non ionizing and ionizing radiation. Matter can be ionized directly and indirectly. Direct ionizing particles are charged particles. They include electrons, protons, alpha particles and heavy ions. (A charged microscopic particle that forms when an ion attaches to a dust mote or similar object). Neutral particles ionize matter indirectly. Neutral particles include photons ( x-rays and Y-rays) and neutrons.
Both of these types of radiation can be harmful, but these both types of radiation are used in treatment of cancer.
The branch of medicine that uses radiation is called radiotherapy.
1. They do not have enough energy to completely remove an electron from an atom or molecule.
Unstable atoms emits radiation. The types of ionization radiation include alhpa radiation, beta radiation, gamma rays, x rays and neutrons
Alpha radiation is the emission of alpha particles during radioactive decay. Radioactive decay is a process of decomposition of a radioactive substance. During alpha decay alpha particles are emitted. Alpha particles consists of two protons and two neutrons bound together into a particles identical to helium nucleus. So alpha decay is simply the emission of helium atom.
e.g. …… the uranium-238 nucleus emits the helium nucleus (that is the alpha particle) and as a result the parent nucleus become thorium-234. Here mass number of parent nucleus (U) has been reduced by 4 and atomic number is reduced by 2. this is one of the characteristic of alpha decay for any nucleus in which it occur.
After emitting the alpha particles the atoms continue to a chain of radioactive decay. During this process atom will be transformed to other isotopes until the atom become non radioactive isotope. (radon, polonium, lead, bismuth) (this is just to show it has chain reaction)
Alpha radiation is the least penetrating. It can be stopped (or absorbed) by a sheet of paper. 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 .
Because they lose all of their energy in a small volume. Alpha particles are effective only for a short distance because they use up their energy when they hit other atoms.
