Gamma ray Definition and 11 Discussions

A gamma ray, also known as gamma radiation (symbol γ or


{\displaystyle \gamma }
), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves and so imparts the highest photon energy. Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900 while studying radiation emitted by radium. In 1903, Ernest Rutherford named this radiation gamma rays based on their relatively strong penetration of matter; in 1900 he had already named two less penetrating types of decay radiation (discovered by Henri Becquerel) alpha rays and beta rays in ascending order of penetrating power.
Gamma rays from radioactive decay are in the energy range from a few kiloelectronvolts (keV) to approximately 8 megaelectronvolts (~8 MeV), corresponding to the typical energy levels in nuclei with reasonably long lifetimes. The energy spectrum of gamma rays can be used to identify the decaying radionuclides using gamma spectroscopy. Very-high-energy gamma rays in the 100–1000 teraelectronvolt (TeV) range have been observed from sources such as the Cygnus X-3 microquasar.
Natural sources of gamma rays originating on Earth are mostly as a result of radioactive decay and secondary radiation from atmospheric interactions with cosmic ray particles. However, there are other rare natural sources, such as terrestrial gamma-ray flashes, which produce gamma rays from electron action upon the nucleus. Notable artificial sources of gamma rays include fission, such as that which occurs in nuclear reactors, and high energy physics experiments, such as neutral pion decay and nuclear fusion.
Gamma rays and X-rays are both electromagnetic radiation, and since they overlap in the electromagnetic spectrum, the terminology varies between scientific disciplines. In some fields of physics, they are distinguished by their origin: Gamma rays are created by nuclear decay, while in the case of X-rays, the origin is outside the nucleus. In astrophysics, gamma rays are conventionally defined as having photon energies above 100 keV and are the subject of gamma ray astronomy, while radiation below 100 keV is classified as X-rays and is the subject of X-ray astronomy. This convention stems from the early man-made X-rays, which had energies only up to 100 keV, whereas many gamma rays could go to higher energies. A large fraction of astronomical gamma rays are screened by Earth's atmosphere.
Gamma rays are ionizing radiation and are thus biologically hazardous. Due to their high penetration power, they can damage bone marrow and internal organs. Unlike alpha and beta rays, they pass easily through the body and thus pose a formidable radiation protection challenge, requiring shielding made from dense materials such as lead or concrete.
Gamma rays cannot be reflected off a mirror and their wavelengths are so small that they will pass between atoms in a detector.

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  1. Strato Incendus

    Can you watch a gamma-ray burst from the side?

    Since gamma-ray bursts travel at the speed of light, my state of knowledge is that, if one were to hit Earth, we would of course only see it the moment it hits us. Furthermore, to my knowledge, we haven’t observed any GRBs within the milky way yet. However, what if there were a GRB within the...
  2. R

    Interpretation of Net Peak Area in Gamma Spectroscopy

    Hello, My question relates to gamma spectroscopy. I understand how the net peak area is calculated for any photopeak. Fortunately, gamma-spec software (e.g., Genie-2000 from Canberra) provides Net peak area and associated uncertainty (for Cs-137 661.7 keV peak, as an example). My question: are...
  3. caters

    High dose gamma ray exposure vs Low dose gamma ray exposure

    I found out that high dose gamma ray exposure is actually easier for the body to repair than low dose gamma ray exposure. At first this made 0 sense to me as higher dose means you are exposed to more gamma rays per second and thus more damage is done. But now that I think about it, I think that...
  4. A

    B Quick Question about emitted radiation and Geiger counter accuracy

    Hi everyone. I read from: that inside the human body, 4400 of K40 atoms disintegrate every second through radioactive decay. Of this decay, 11% (480) results in gamma radiation, and 50% of that 11% (240) escapes the body. My...
  5. R

    Energy of the photon emitted in a gamma ray decay

    Homework Statement An Fe nucleus (A=57) decays from an excited stated to the ground state by emitting a gamma ray. The energy of the photon is 14.4 KeV when the nucleus is held fixed. If the nucleus is free to recoil then the energy of the photon emitted will be? Homework Equations ## E =...
  6. U

    I Background gamma radiation

    I'm trying to find out how much gamma-radiation the average human is exposed too from background radiation. But all I can find are numbers describing the total background radiation, not just the gamma radiation alone. Does anyone know where I can find this information?
  7. moenste

    Minimum safe distance from a radioactive source

    Homework Statement The potassium isotope 4219K has a half-life of 12 hr, and disintegrates with the emission of a γ-ray to form the calcium isotope 4220Ca. What other radiation besides γ-rays must be emitted? How many electrons, protons, and neutrons are there in an atom of the calcium isotope...
  8. N

    Stargazing H.E.S.S. gamma ray telescope got an image of the moon Can we use better telescopes of this type (ground based gamma rays telescopes) to image the surface and subsurface of a planet with a lot of resolution?
  9. ryanuser

    New: Quantum teleportation

    Hi Would it be possible to force an electron and a positron to meat each other and annihilate, then the gamma beam created is to be directed some distance away and passed next to an atom for pair production to occur. ( I dismissed complications related to the vacuums and the magnetic fields)...
  10. nurul anuar

    High purity germanium detector

    hi there! I am nurul ain,new member here. I have a question regarding gamma ray detector, the high purity germanium detector or aka HPGe. What is meant by the detection efficiency at specific gamma-ray energy (εγ)? and whether the emission probability of the corresponding gamma-ray energy and...