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Gamma rays
gamma ray , electromagnetic radiation of the shortest wavelength and highest energy. Gamma rays are produced in the disintegration of radioactive atomic nuclei and in the decay of certain subatomic particles. The term gamma ray was coined by British physicist Ernest rutherford in 1903 following early studies of the emissions of radioactive nuclei. When an unstable atomic nucleus decays into a more stable nucleus, the “daughter” nucleus is sometimes produced in an excited state. The subsequent relaxation of the daughter nucleus to a lower-energy state results in the emission of a gamma-ray photon. Gamma rays are also produced in the important process of pair annihilation, in which an electron and its antiparticle, a positron, vanish and two photons are created. The photons are emitted in opposite directions and must each carry 511 keV of energy—the rest mass energy of the electron and positron. Gamma rays can also be generated in the decay of some unstable subatomic particles, such as the neutral pion. There are several physical processes that generate cosmic gamma rays:
- A high-energy particle can collide with another particle
- A particle can collide and annihilate with its anti-particle
- An element can undergo radioactive decay
- A charged particle can be accelerated
A high-energy particle can collide with another particle
In gamma-ray astronomy, "particle-particle collision" usually means a high- energy proton, or cosmic ray, strikes another proton or atomic nucleus. This collision produces, among other things, one or more neutral pi mesons (or pions). These are unstable particles that decay into a pair of gamma rays.
A particle can collide and annihilate with its anti-particle
A particle and its anti-particle, such as an electron and a positron, will undergo something called an annihilation process. In physics, this process produces neutral pions that quickly decay into gamma rays.
An element can undergo radioactive decay
Radioactive decay results when an element changes to another element by virtue of changes within the atom's nucleus. These changes leave the nucleus in an excited state. The atom emits a gamma ray as it decays into the ground state. Radioactive gamma-ray sources in space are associated with events of nucleosynthesis, such as supernovae.
A charged particle can be accelerated
A magnetic field exerts a force on a charged particle that is moving in it. This causes the particle to radiate, with the emitted power being proportional to the square of the force divided by the square of the mass of the particle. For electrons, this radiation is often in the gamma-ray region of the electromagnetic spectrum. The character of the radiation (and the name given to it) depends on the nature of the accelerating force. If the electron is accelerated in the electrostatic field around a nucleus, the resulting radiation is called bremsstrahlung ; it is synchrotron radiation (sometimes also called cyclotron radiation) when the acceleration takes place in a static magnetic field; and the process is called or Compton scattering (sometimes also called Thomson scattering) when the acceleration occurs in the electromagnetic field of a photon.
Properties of gamma rays
Gamma rays are a form of Electromagnetic radiation[EMR]. They are the similar to X-rays, distinguished only by the fact that they are emitted from an excited nucleus. Electromagnetic radiation can be described in terms of a stream of photons, which are massless particles each travelling in a wave-like pattern and moving at the speed of light. Gamma-ray photons have the highest energy in the EMR spectrum and their waves have the shortest wavelength. Scientists measure the energy of photons in electron volts (eV). Gamma-ray photons generally have energies greater than 100 keV. The high energy of gamma rays enables them to pass through many kinds of materials, including human tissue. Very dense materials, such as lead, are commonly used as shielding to slow or stop gamma rays. Gamma rays are high-recurrence electromagnetic waves without mass and charge. This radioactive outflow has the minimal force of
Health effects of exposure to gamma radiation
Gamma radiation is highly penetrating and interacts with matter through ionisation via three processes; photoelectric effect, Compton scattering or pair production. Due to their high penetration power, the impact of gamma radiation can occur throughout a body, they are however less ionising than alpha particles. Gamma radiation is considered an external hazard with regards to radiation protection. Similar to all exposure to ionising radiation, high exposures can cause direct acute effects through immediate damage to cells. Low levels of exposure carry a stochastic health risk where the probability of cancer induction rises with increased exposure.
Sources of gamma rays
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. 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.
Uses of gamma ray
Gamma rays are a form of electromagnetic radiation and are used in medicine to treat cancer. These rays have the ability to penetrate deep into the human body, which makes them great for targeting specific tumours.
Gamma rays are also used in medical imaging, such as Computed Tomography (CT). This is a process that is performed by doctors to get an accurate view of a patient's brain or another part of the body. Doctors use CT scans to diagnose many diseases and conditions. Gamma rays are a form of radiation that can be emitted by radioactive substances such as uranium, plutonium and cobalt. They can also be produced artificially from radioactive isotopes. Uses of cobalt-60: Pasteurisation, via irradiation, of certain food stuffs, levelling or thickness gauges (i.e. food packaging, steel mills). Industrial radiography, sterilisation of medical equipment in hospitals Uses of caesium-137: measurement and control of the flow of liquids in industrial processes. investigation of subterranean strata (i.e. oil, coal, gas and other mineralisation). measurement of soil moisture-density at construction sites. levelling gauges for packaging of food, drugs and other products. Uses of technetium-99m: Tc-99m is the most widely used radioactive isotope for medical diagnostic studies different chemical forms are used for brain, bone, liver, spleen and kidney imaging. It is also used for blood flow studies. Uses of americium-241: smoke detectors for households. fluid levelling and density gauges. thickness gauges for thin materials (i.e. paper, foil, glass)aircraft fuel gauges. when mixed with beryllium, americium-241 produces a 241 AmBe neutron source with uses in well logging, neutron radiography and tomography.
