Presented by: Fathimath Shibana
First semester 2012
University of Mysore
Guided by: Dr. H.S. Aparna
DOS in Biotechnolog
It is defined as the process by which
energy is emitted from a source and
propagated through the surrounding
Radioactivity : It is the act of emitting radiation
spontaneously from the unstable
Unstable atoms differ from stable atoms
because they have an excess of energy or mass
Unstable atoms are known as radioactive
E.g. Carbon 14, Uranium 238
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
radio waves, etc
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.
TYPES OF IONIZING RADIATION
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.
Alpha radiation travels a very short distance
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
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.
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.
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
Characteristics of beta radiation:
Beta radiation may travel meters in air and is moderately
It can penetrate human skin
to “germinal layer” where new
cells are produced.
Beta emitting contaminants may be harmful if deposited
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.
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.
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
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.
Gamma radiation is electromagnetic radiation of high
frequency and therefore high photons with a very short
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.
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.
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
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
Gamma radiation or X-rays frequently accompany the
emission of alpha and beta radiation
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
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.
The most common tracer is called Technetium-99 and is very
safe because it only emits gamma rays and doesn't cause
• 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
• 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.
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
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.
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.