GAMMA RAYS

GAGAN
 INTRODUCTION

• High-energy, short-wavelength, electromagnetic radiation

emitted from the nucleus of an atom. Gamma radiation
frequently accompanies emissions of alpha particles and beta
particles, and always accompanies fission. Gamma rays are
similar to x-rays, but are very penetrating and are best stopped
or shielded by dense materials, such as lead or depleted
uranium
• Gamma-ray radiation have wavelengths that are
generally shorter than a few tenths of an angstrom
(10−10 metre) and gamma-ray photons have energies
that are greater than tens of thousands of electron volts
(eV). There is no theoretical upper limit to the energies
of gamma-ray photons and no lower limit to gamma-
ray wavelengths; observed energies presently extend
up to a few trillion electron volts—these extremely
high-energy photons are produced in astronomical
sources through currently unidentified mechanisms.
 DISCOVERY
• The term gamma ray was coined by British physicist Ernest
Rutherford in 1903 following early studies of the emissions of
radioactive nuclei
• Paul Villard, a French chemist and physicist, discovered
gamma radiation in 1900 while studying radiation emitted by
radium.
 SOURCES OF GAMMA RAYS

• Gamma rays have the smallest

wavelengths and the most energy of
any wave in the electromagnetic
spectrum. They are produced by the
hottest and most energetic objects in
the universe, such as neutron stars
and pulsars, supernova explosions,
and regions around black holes. On
Earth, gamma waves are generated by
nuclear explosions, lightning, and the
less dramatic activity of radioactive
decay.
 SOME COMMON SOURCES OF GAMMA
RADIATION

• Gamma radiation is released from many

of the radioisotopes found in the natural
radiation decay series of uranium,
thorium and actinium as well as being
emitted by the naturally occurring
radioisotopes potassium-40 and carbon-
14. These are found in all rocks and soil
and even in our food and water.
• Artificial sources of gamma radiation
are produced in fission in nuclear
reactors, high energy physics
experiments, nuclear explosions and
accidents.
 DETECTING GAMMA RAYS
• Unlike optical light and x-rays, gamma rays
cannot be captured and reflected by mirrors.
Gamma-ray wavelengths are so short that
they can pass through the space within the
atoms of a detector. Gamma-ray detectors
typically contain densely packed crystal
blocks. As gamma rays pass through, they
collide with electrons in the crystal. This
process is called Compton scattering, wherein
a gamma ray strikes an electron and loses
energy, similar to what happens when a cue
ball strikes an eight ball. These collisions
create charged particles that can be detected
by the sensor.
 MEDICAL APPLICATIONS OF GAMMA
RAYS
• Medical applications of gamma rays include the
valuable imaging technique of positron emission
tomography (PET) and effective radiation
therapies to treat cancerous tumors.
• Radiation therapies make use of this property to
selectively destroy cancerous cells in small
localized tumors. Radioactive isotopes are
injected or implanted near the tumor; gamma
rays that are continuously emitted by the
radioactive nuclei bombard the affected area
and arrest the development of the malignant
cells
USES OF GAMMA RAY EMITTERS
Uses of cobalt-60: Uses of caesium-137:
• sterilization of medical equipment in • measurement and control of the flow of
hospitals liquids in industrial processes

• pasteurization, via irradiation, of • investigation of subterranean strata (i.e. oil,

coal, gas and other mineralization)
certain foodstuffs
• measurement of soil moisture-density at
• levelling or thickness gauges (i.e. food
construction sites
packaging, steel mills)
• levelling gauges for packaging of food, drugs
• industrial radiography. and other products.
Uses of technetium-99m: Uses of americium-241:
• Tc-99m is the most widely used • smoke detectors for households
radioactive isotope for medical diagnostic • fluid levelling and density gauges
studies
• thickness gauges for thin materials (i.e.
• different chemical forms are used for paper, foil, glass)
brain, bone, liver, spleen and kidney
imaging. It is also used for blood flow • aircraft fuel gauges
studies. • when mixed with beryllium, americium-
241 produces a 241AmBe neutron source
with uses in well logging, neutron
radiography and tomography.
 NCERT

• They lie in the upper frequency range of the

electromagnetic spectrum and have wavelengths of from
about 10–10m to less than 10–14m. This high frequency
radiation is produced in nuclear reactions and also
emitted by radioactive nuclei. They are used in medicine
to destroy cancer cells.
THANK YOU