What is Gamma ray: Definition and 129 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

    Writing: Input Wanted Can a Gamma-Ray Burst Affect Communication Devices?

    There have been quite a few threads on gamma-ray bursts already, so I’ll make this one as specific as I need it for my WIP sci-fi story: Can a gamma-ray burst that affects the entire solar system, among others, damage the majority (if not all) devices capable of interstellar communication? For...
  2. P

    B Amaterasu and GRB221009A: A Comparison of Cosmic Rays and Gamma Ray Bursts

    Can this Amaterasu particle and GRB221009A be compared against each other? The former is always noted as a gamma ray (singular), nowhere have I read it being referred to as a gammy-ray burst, however. Does this mean scientists have detected this one lone gamma ray and only one? [Edit/Update: I...
  3. B

    B Gamma Ray Burst / Jet Questions

    The 1st photo is a Google image of a Gamma ray Burst in space, the image in the other photo is being emitted from a device I am playing around with. I am just wondering what is the cause of or what dictates the behavior of actual Gamma Ray Bursts in space vs whatever light patters are in the...
  4. 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...
  5. 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...
  6. D

    B Supernova Gamma Ray: 6000 Light Year Journey

    I'm watching an episode of "How the universe works" and they explained the nightmare scenario where a star supernovas and turns into a black hole, emitting such a powerful burst of gamma rays, that if it were any closer than 6000 light years then it would be capable of stripping the entire Earth...
  7. 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...
  8. A

    I Latest Gamma Ray Burst Experimental results

    with regards to this https://arxiv.org/abs/1103.5626 "Gamma ray burst delay times probe the geometry of momentum space" May we have updates of the latest experiment results along the line of Smolin 2011 idea concerning gamma ray burst delay times that can test if momentum space is curved?
  9. O

    I U-235 thermal neutron capture gamma ray

    Hi, When U-235 captures a neutron, it may end up with a fission reaction or an excited U-236 isotope. This U-236 emits gamma rays as it goes to its ground state. What I want to learn is that how much is the contribution of these gamma rays' energy to overall fission energy. I checked the...
  10. H

    Two parallel opposed Co-60 Gamma Ray beams in Excel

    Hi everyone, I have this question about POP. Assume a patient separation of 20cm. Using data for 6MV , FS 10x10 cm, plot the depth dose for one beam at 2 cm intervals. Include on your plot the dose at dmax and the dose at 20-dmax. On the same graph repeat this for the opposed beam. Now plot the...
  11. A

    B Quick Question about emitted radiation and Geiger counter accuracy

    Hi everyone. I read from: https://www.nucleonica.com/Applet/NaturalRA/Button5/page5.html 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...
  12. A

    Linear attenuation coefficient for gamma ray attenuation

    Homework Statement I have data for the count rate (of gamma rays) against the thickness of various materials (Al, Pb, Fe etc...). I want to work out the linear attenuation coefficient. Can I do this by plotting the natural log of count rate against thickness? I don't have values for...
  13. G

    Gamma ray irradiation and a shielded chamber question

    Hi I was reading an article about a gamma ray materials testing camera built into one of the research reactors that worked in my country a while ago. Now I have a few questions regarding some of the issues the article wasn't informing about. It says that they built a special enclosed and...
  14. Adam Rabe

    Percentage transmittance gamma ray through lead

    Homework Statement Homework Equations I = Io e^-ux The Attempt at a Solution 0.75 = 1 * e^-u1 using algebra... u =2.117 I = 1 * e^-2.117*3 I = 0.00175 Answer is apparently 42.2. Can someone tell me where i went wrong? Thanks for any help as always
  15. Daniel Petka

    B Energy of Gamma Ray Photon with Wavelength h

    What would be the energy (eV) of a gamma ray photon with the wavelength h (Planck's length)?
  16. P

    I Gamma ray cross sections from classical plane wave

    I am aware that in classical electrodynamics a metal exponentially attenuates TEM waves. I am wondering if this fact is sufficient to obtain estimates of the cross section of low energy gamma rays in metals. Obviously it would fail for higher energy gamma rays where Compton scattering and pair...
  17. 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 =...
  18. P

    According to Maxwell, a gamma ray can be as energetic as a radio wave (given equal E amplitudes)?

    According to the old thery of light the energy carried by by a wave is proportional to the amplitude of the electric field not to the frequency as Planck proposed, so an eletromagnetic radiation in the gamma spectrum carry the same energy as a radio one if their amplitude is the same? They only...
  19. 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?
  20. M

    B Is the Gamma Ray Burst Diameter Wide Enough to Engulf Our Solar System?

    Is it true gamma ray burst diameter can be as big as the solar system and the sky would become bright with its light even if it is 4000 light years away? Saw this at History Channel.
  21. Clara Chung

    How does a gamma ray get converted to visible light

    In the process of heat transfer from core to photosphere, each gamma ray in the Sun's core is converted during scattering into several million visible light photons before escaping into space.----from Wikipedia How does heat transfer related to scattering? Is it related to Raman scattering as...
  22. Clara Chung

    B What is the recommended method to reduce gamma ray exposure?

    A gamma ray source emits gamma ray to a photographic plate in a container. The book said the blacked region on the photographic plate wouldn't be affected if the gas pressure of the container was increased. However, I think that the gamma ray will ionise more air molecules and lose more energy...
  23. 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...
  24. Sebastiaan

    Using Gamma Ray reflector to reduce mass of Shadow shield

    Let's say we have manned space vessel powered by a highly power but radioactive rocket engine, producing a lot of deadly gamma rays. The classical answer to this problem is to use a shadow shield. However, Nuclear Shadow Shields are very heavy. What about the idea of instead of trying to absort...
  25. C

    Why don't we have gamma ray microscopes?

    Homework Statement Why? We can use shorter wavelengths than that of electrons to view electrons and more? What is stopping us? Can the image not be imprinted on a plate of some sort instead of being viewed by the eye directly? Homework Equations none The Attempt at a Solution I'm guessing no...
  26. CapnGranite

    Effects of a gamma ray burst on earth

    http://phys.org/news/2016-10-deadly-nearby-gamma-ray.html How deadly would a nearby gamma ray burst be? The original paper in Astrobiology is locked, but this summary is pretty complete. "A burst at the South Pole fits in with theories of the Ordovician extinction because the measured...
  27. N

    Stargazing H.E.S.S. gamma ray telescope got an image of the moon

    https://en.m.wikipedia.org/wiki/File:Moon_egret.jpg 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?
  28. EBPoncho

    PET/CT Gamma Ray Protection with Lead Apron

    I was informed I might get a better response by posting to this forum, so sorry for the double post. Hello all, I am currently attending a service course for a PET/CT system for my employer. We have been covering the physics behind the function of detectors and my instructor said something...
  29. S

    Determining Gamma Ray energy from spectrum

    Homework Statement (Preface: I am not a physicist) The pulse height spectrum of a radioactive source known to emit high energy photons was measured using a small detector. Three distinct peaks were observed at heights of 7.38, 6.49 and 5.60 V, along with a continuous portion of the spectrum...
  30. Developer_CM

    Gamma Ray Spectroscopy - 97 keV Peak for U238 Metal

    I recently acquired a 39 gram sample of U-238 metal. I ran a gamma spectrum on the sample and found a major peak around 97 keV. I couldn't find any documents that mentioned this peak for U-238, but it is very prominent. I ran a gamma ray spectrum on a 5 gram Uranium Oxide sample and it also...
  31. Jonathan Scott

    A Gamma ray burst associated with LIGO GW event

    Quite unexpectedly, it seems that the Fermi Gamma-ray Burst Monitor spotted what appears to be a hard gamma-ray burst about 0.4s after the LIGO GW event, lasting about 1s: http://arxiv.org/abs/1602.03920 This is not expected from a black hole merger (and as a black hole sceptic, I find it very...
  32. A

    The mechanics of gamma ray bursts

    I've been googling explanation for gamma ray bursts but couldn't find any that explain how and why the jets actually form, in one website I read that the jets have to be there to "carry off momentum and keep the black hole from spinning too fast", and no other details are mentioned in that...
  33. DiracPool

    Pair Production and gamma ray

    Pair Production questions: 1) When a gamma ray photon pair produces an electron and a positron, do the two particles always have the opposite spin? That is, one always has +1/2(h-bar) spin and the other has -1/2(h-bar) spin? 2) Other than charge and spin, what are some other notable...
  34. M

    X-Ray vs Gamma Ray: What's the Difference?

    My question is, if X-Ray and Gamma rays overlap in the EMR spectrum, then how can they be classified differently. I have read about different energy levels but I'm just afraid I'm missing something is that the only difference?
  35. anorlunda

    Fermi gamma ray detector

    Today's APOD shows an animated visualization of a gamma ray flare detected by The Fermi Space Telescope. The video says, "each circle represents one gamma ray" That language suggests single photon detection. Is that correct?
  36. S

    Gamma ray energy spectrum

    Hi every one, What is the smooth gamma ray energy spectrum in gamma radiation? And, What is the algorithm of smooth gamma spectrum? Thank every one to much!
  37. N

    Energy of Gamma ray = hf?

    Hello everybody, In one of my assignments I have lost a substanial portion of the grade for one problem because I haven't assumed that the energy of a Gamma ray = hf, I thought this was wrong, and that nothing in the statement says that it consists of only one photon. In fact, it says "high...
  38. 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)...
  39. 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...
  40. jim mcnamara

    Reticulum 2 - gamma ray emissions

    http://arxiv.org/pdf/1503.02320v1.pdf This paper discusses the emission of gamma rays from a neighboring dwarf galaxy. My understanding is that there is no conventional explanation of gamma ray emission. So there is interest in pursuing a possibility that these emissions are from dark matter...
  41. D

    Problem integrating gamma ray absorption model

    Homework Statement In this lab various thicknesses of a few materials are placed between a source of gamma radiation and a couple different detectors. It is reasonable to assume that some small change in the thickness of the shielding would produce a proportional change in the intensity of the...
  42. ryanuser

    Gamma ray: energy reduction

    Hi, my question is that would it be possible to reduce the energy and frequency of gamma rays to visible light then maintain it at that level?
  43. Qw_freak

    Calculation of gamma ray shielding value in liquids?

    Hi folks Please bear with me, I'm new here and this may not be the correct forum to ask this question. If this is the case, I'll of course remove my question and ask it the appropriate place instead. However, here it goes: I need to be able to calculate how much a given intensity of gamma...
  44. H

    Skin Effect VS Gamma Ray

    Skin Effect: . where = resistivity of the conductor = angular frequency of current = 2π × frequency = relative magnetic permeability of the conductor = the permeability of free space ------------------------------ From Wiki According to Skin Effect, the higher the frequency, the less...
  45. Spinnor

    1 dimensional crystal at rest, a nucleus emits gamma ray of energy E,

    Say we have a one dimensional chain of N mass points separated by springs of spring constant k. This system can be quantized? Let the quantized system above be at rest and let one of the end mass points emit a photon of energy E along the crystal axis. Will we get physics similar to he...
  46. marcus

    Gamma ray bursts (GRB) and distribution of life

    Gammaray bursts (GRB) may affect the prevalence of life in various different regions of the galaxy. http://arxiv.org/abs/1409.2506 On the role of GRBs on life extinction in the Universe Tsvi Piran, Raul Jimenez (Submitted on 8 Sep 2014) As a copious source of gamma-rays, a nearby Galactic...
  47. K

    Gamma Ray Burst datasets that consist of distance modulus & redshift

    Hi guys I am looking for a dataset to use in my thesis. I am working on UNION 2.1 sample of supernovea Ia data. That dataset consist of redshift and distance modulus with uncertainty (sigma) for 590 supernovea. Do you guys know where can i find similar dataset for GRBs?
  48. D

    Gamma ray and Xray to RF?

    Hi guys, Could someone refer me to sources which explain and give examples for crystals which absorb xray / gamma ray and emit RF ? Meaning that if I radiate a crystal with xray I get RF so I can theoretically track its movement in the enclosed are. Thanks a lot!
  49. |Glitch|

    Gamma Ray Burst GRB 130427A: The Brightest Explosion in the Universe

    I recently read the following article: It was not very long, and it did not contain much information. However, after a little searching I discovered the article was referring to GRB 130427A. The key features of this GRB are its strength at 94 GeV, and its duration at "better part of a...