What is Gamma rays: Definition and 99 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. kvidtr

    Can Geiger Counter Ticks be converted into particle/wave counts?

    TL;DR Summary: Currently working on a project for lab where we're sending Geiger counters 100k feet into the air. Goal is to determine radiation as a function of altitude. Need some guidance. Hi everyone, I'm currently working on a project for lab where we're sending Geiger counters 100k feet...
  2. cemtu

    A Why KE of Annihilation Electrons Differs?

    We know that when a high energy gamma ray(E >= 1022 keV because the total energy of 1 electron at rest and 1 positron at rest is 511 keV) passes near a high Z(atomic weight) atomic nucleus interacts with the electrical field of the nucleus and there is a probability that this high energetic...
  3. Graham87

    Troubleshooting Nuclear Reactions: Decay, Gamma Rays & More

    The problem comes with solutions. However, I dont get the 3 steps in the solutions. Why do they calculate decay for 120min in step 3? And why is only the daughter nuclide relevant and no granddaughter? There might be something lacking in my knowledge about nuclear reactions. Also, I don't know...
  4. osaplabs_sja

    A Can any thin materials protect a Mars spacecraft from gamma rays?

    Astronauts heading towards Mars (and hopefully return) will need protection against the harmful effects of gamma rays in space for this long trip. Apparently, much shorter trips have not caused enough bodily harm to be of much concern. However, a 6-month or longer trip might be a real problem. I...
  5. R

    B Distance covered when 22 MeV gamma rays travel through air

    Both alpha and beta radiations can only travel short distances through air as they're not as penetrating as gamma radiations. How long gamma radiations with 22 MeV energy can travel in air? Is it meters, kilometers, miles, etc. Is there a difference between a lower energy gamma ray and a higher...
  6. R

    B Which one is more efficient in generating high energy Gamma rays?

    According to https://apps.dtic.mil/dtic/tr/fulltext/u2/a351472.pdf the big pulsed power accelerator, HERMES III, generate electron beam with peak energy at 22 MeV and average electron energy at 16 MeV and the resulting photon energy which is bremsstrahlung radiation is approximately 2 MeV...
  7. R

    Differences between X-rays and Gamma rays

    Some people said if it is originated from electrons then it is X-ray but if it is originated from the nucleus it is Gamma ray. But people can produced X-rays and Gamma rays by Bremsstrahlung process and in Bremsstrahlung process it is resulted from decelerating or braking electrons. So, Gamma...
  8. R

    B Gamma rays over very large areas

    According to this link https://apps.dtic.mil/dtic/tr/fulltext/u2/a351472.pdf, HERMES III at Sandia National Labs can generate very large area gamma rays by converting the electron beam into bremsstrahlung radiations after hitting the tantalum target. As we can see in the isodose contours in the...
  9. R

    How far do gamma rays extend from an accelerator?

    According to https://www.osti.gov/servlets/purl/7234564, the HERMES III which stand for High Energy Radiation Megavolt Electron Source accelerator is "capable of delivering a peak dose of ~100 krad (CaF2) over a useful area of ~1000cm2 (area where dose is greater than 50% of the peak dose) in a...
  10. PainterGuy

    I Beta and gamma rays from radium

    Hi: Source: https://en.wikipedia.org/wiki/Radium Question 1: I think that the first statement suggests that it's the emission of alpha particles, beta particles and gamma rays which raises the temperature of radium sample; possibly on their way out from the sample, those particles and gamma...
  11. N

    B What happens when gamma rays with ultra-high energies interact with matter?

    What sort of properties would you expect from gamma rays, as you increase their energy, and why? Would they penetrate high Z-matter more easily? What would be the outcome of the interactions? Do you expect photoelectric and Compton scattering processes to become negligible, and the dominant...
  12. N

    Question about proportional counters for gamma rays

    I understand the concept that a more energetic photon would cause more ionization events and therefore we can estimate the original energy of the incident photon. But what I don't get is that in practice, you don't get one photon entering the detector at a time, you get a whole bunch of them...
  13. D

    I Can Laser Pulses Produce MeV Gamma Rays?

    i already know radioactivity produces gamma rays. Are there other ways to produce gamma rays in a laboratory, without radioactive substances?
  14. I

    I What would happen if wavelength could go higher than gamma rays

    We can see wave length that get compress and get higher in height when they get high energy so how would wavelength react and it how it would look like when it gets high amount of energy(like infinite energy)?
  15. D

    How short can electromagnetic radiation become? Shorter than gamma rays?

    is there some physical limit on the wavelength of electromagnetic radiation? Can there be radiation shorter than gamma rays?
  16. C

    I The Sun's excess gamma rays and strange dips

    Any theory what could be causing the excess gamma ray and the strange dips in the sun? https://www.quantamagazine.org/gamma-ray-data-reveal-surprises-about-the-sun-20190501/ "A decade’s worth of telescope observations of the sun have revealed a startling mystery: Gamma rays, the highest...
  17. TheBigDig

    Energy of Two Gamma Rays Produced by Pion Decay

    So I worked out the first part and obtained ##E_1 = 478.8MeV##, ##E_2 = 459.4MeV## and ##p = 0.49 MeV/c## but I can't quite wrap my head around the second part. Normally, I'd use the equation for s but I'm confused since I don't know the angle between the gamma rays.
  18. S

    B Double Slit Experiment with Gamma Rays

    Hi I was wondering what would happen if you use Gamma Rays in a double slit experiment. Would you see the same interference pattern?
  19. KangOfCanada

    A How do Fusion/Fission Gamma Rays Compare?

    My concerns are all about how much shielding would be needed for a nuclear reactor. Would aneutronic He3-He3 fusion produce less energetic photons than fission to be more easily used in more mobile reactors? Obviously very few neutrons are made in this reaction so that leaves the high energy...
  20. A

    B If you are exposed to radiation, do you emit it?

    Hi everyone. I was thinking about the question that I stated in the title. If you are exposed to radiation, such as alpha and beta particles, you don't emit radiation. The alpha particles are merely stopped because they don't have a high penetration. The beta particles pass through your body and...
  21. Sebastiaan

    A How to calculate the energy of Gamma rays in fusion

    Lets say you have your basic fusion reaction D + H → He3 + γ + 5.49 MeV Now exactly how much of the energy is carried away by the gamma ray and how much by the Alfa particle ?
  22. R

    Could there be life that thrives in gamma rays?

    I am not sure if this is entirely correct, but first I am going to say that life on Earth mostly thrives in the visible range of the electromagnetic spectrum, and perhaps some infrared and ultraviolet (for some creatures), because it is the frequency range that they were the most exposed to...
  23. J

    I How to derive full solar sprectrum from gamma rays

    I understand that the fusion of hydrogen to helium in our sun's core generates gamma rays. My question is how are these gamma rays transformed to the full spectrum of photons that we that we observe from earth?
  24. N

    I How to determine the energy of photons released in decay

    What equation would I need to use to determine the energy of photons released when radio-isotopes decay? I would like to figure out the energies of photons released when tritium and plutonium 237 decay.
  25. Jonathan Scott

    A Could gamma rays imply GW sources not black holes?

    When I saw the report of a gamma ray burst associated with the LIGO GW event, my immediate thought was that the obvious explanation is that the compact massive objects were not in fact black holes, and the gamma ray burst was from the energy of the final collision and merger. This would...
  26. N

    Can multicellular life be sustained with gamma rays?

    If there are bacteria that can get their energy from gamma rays (thus thriving on nuclear reactors), can multicellular life do it too? If so, wouldn't that broaden the parts of the universe where life could arise?
  27. wolram

    Gamma rays unlikely to originate from Dark Matter

    If we can not use gamma rays to detect Dark Matter what can we use? http://www.sciencedaily.com/releases/2016/02/160203110928.htm Studies by two independent groups from the US and the Netherlands have found that gamma ray signals from the inner galaxy come from a new source rather than from...
  28. Sebastiaan

    Radiation Damage In metals from Gamma rays

    From my understanding gamma rays can damage metal, making it brittle. Fortunaly, this appears to be little, but sill if you have a lot (like in p-D fusion) it becomes a serious hazard. The question is, how much? Specificly I need to know how much damange it does in compairison to Neutron...
  29. V

    Dark matter annihilation into gamma rays

    This question straddles this forum and the "Beyond the Standard Model" one a bit, so if a mentor thinks it belongs better elsewhere, please feel free to move it. I've seen references in the "popular science" press about the possibility of indirectly detecting dark matter by looking for gamma...
  30. ryanuser

    Splitting Gamma-Ray Photons: Is It Possible?

    Is there a way to split gamma-ray photons into less energetic photons? And is the opposite possible, by combining low energy photons into a high energy one?
  31. A

    Why must an electron-positron collision produce gamma rays?

    Or, more specifically, what determinates the frequency of the photons emitted by a such a collision. I know that the number of photons produced depends on the spin and energy states of the initial particles.
  32. Z

    Will electron create gamma-radiation?

    If we put cathode rod with enormouse voltage in vacuum between strong magnetic fields pointing down parallel to rod end then put electron in it with initial speed equal to speed of light and begin circling around cathode, Will electron make gamma -rays according to synchrotron radiation?
  33. D

    Help Solving Physics Exam Question on Gamma Rays Counting Rate

    Hi, I came across a question in an exam which I couldn't really relate to any topic of physics, that I had studied. It goes like this- A detector is used to count the number of gamma rays emitted by a radioactive source. If the number of counts recorded in exactly 20 seconds is 10000, the...
  34. T

    Gamma rays induced fission of silicon

    Hey everyone I'm new here and this is my first thread, although i have great interest in chemistry and physics my knowledge of these fields is very basic( I'm graduated in economics) so don't be surprised if i ask something that may look silly. so here are my firsts questions. -Is it...
  35. C

    Pion Decay into Gamma rays angle

    So i have a question regarding a homework question I'm working on which suggest a neutral pion traveling with velocity v decays into two gamma rays of equal theta to the normal and they of course have velocity c. It then asks to prove that v= cos theta Which kind of confuses me. I mean if...
  36. M

    Why isn't there Cosmic Visible Background Radiation from gamma rays?

    If what used to be visible light when the universe was smaller and younger has been stretched due to the Doppler effect so that it is now microwaves and detectable as the Cosmic Microwave Background Radiation that can be found everywhere, why hasn't the gamma or x-rays of the same period not...
  37. J

    What is the Physical Reason for Gamma Rays Being Absorbed?

    But high frequency are absorbed, like gamma rays. I would think it would be the opposite. So what's the physical reason?
  38. J

    So why does the atmosphere block gamma rays but not UV rays?

    Or light rays for that matter. Where does the window open in the atmosphere on the em spectrum, UV? Why is that?
  39. F

    Are Gamma Rays Always Part of Nuclear Reactions?

    Making it short : Do gamma rays ALWAYS accompany a nuclear reaction?? I was thinking, since there are only three types of radioactive decay, alpha, beta and gamma. I don't quite understand how gamma radiation will always occur. Isn't it going to be just ONE of the three types? /Help :)
  40. S

    Calculating Gamma Ray Count Rate Error in 20 secs

    Homework Statement A detector is used to count the number of gamma rays from a radioactive source if the number of counts is 10000 in exactly 20 secs then what is the error in counting rate per sec? Homework Equations- no idea. The Attempt at a Solution- As per our syllabus we...
  41. M

    Simulate Gamma Rays from Radioactive Decay

    Hello, I am trying to simulate the gammas from certain radioactive decays but I am really puzzle as to how to approach this. The site I'm using as a reference lists the intensities of the different gammas corresponding to an specific decay. The thing that confuses me is that, for example...
  42. J

    Can gamma rays be deflected or shielded against with an electromagnetic field?

    I know we can contain the energy/plasma from a fussion reaction with an electromagnetic field, but would an EMF protect from gamma rays? Would it be possible to deflect a nuclear blast with a powerful enough EMF?
  43. lpetrich

    Evidence of Dark Matter? 130-GeV gamma rays from near our galaxy's core

    The Reference Frame: A confirmation of the 130 GeV dark matter-like bump - Lubos Motl [1204.2797] A Tentative Gamma-Ray Line from Dark Matter Annihilation at the Fermi Large Area Telescope - Christoph Weniger [1205.1045] Fermi 130 GeV gamma-ray excess and dark matter annihilation in...
  44. E

    Pion decays into gamma rays. Find the energy and angle

    Hi all, I was having trouble with this problem and hoping that someone could help me with it. A pion has a rest energy of 135 MeV. It decays into two gamma rays, bursts of electro magnetic radiation that travel at the speed of light. A pion moving through the laboratory at v = 0.97c decays...
  45. Dotini

    No Obvious Objects Produce Gamma Rays

    http://science.nasa.gov/science-news/science-at-nasa/2011/18oct_600mysteries/ "Fermi sees gamma rays coming from directions in the sky where there are no obvious objects likely to produce gamma rays," says David Thompson, Fermi Deputy Project Scientist from Goddard Space Flight Center...
  46. Dotini

    Surprising Gamma Rays From Crab Nebula

    http://www.bbc.co.uk/news/science-environment-15203788 Astronomers have spotted gamma ray emissions coming from the Crab Pulsar at far higher energies than expected. This challenges notions of how these powerful electromagnetic rays - like light, but far more energetic - are formed, researchers...
  47. J

    Light & Gamma Rays: Why Does One Penetrate and Not the Other?

    Hi everybody, We know that light is an electromagnetic wave.gamma rays are e.m.waves. Both of them have the same speed 3*10^8 m/s. Gamma ray have the property to penetrate in materials like wood,cement wall etc. But,light is not penetrating even in a single wood. What is the reason behind...
  48. Z

    Vacuum Energy Form (aside from gamma rays)

    So apparently vacuum energy is created and destroyed within Planck time by matter, antimatter annihilation. If someone could theoretically stop or slow down time, would it be possible to tap into vacuum energy? Since annihilation creates gamma rays, I suppose vacuum energy would face the same...
  49. Ryan_m_b

    Reflecting Gamma Rays w/ Electron Gas for Spacecraft

    In a discussion recently I came across the idea of an antimatter photon rocket, to quote http://en.wikipedia.org/wiki/Nuclear_photonic_rocket#Power_sources" Looking through various sites via google I've had a few answers as to how gamma rays may be reflected, the general consensus is that it...
  50. bcrowell

    Dark matter: gamma rays, direct detection, and solar-system tests

    Here are some recent papers on attempts to detect dark matter directly or indirectly: a solar system test with a possible positive result: http://arxiv.org/abs/1001.1697 direct detection, with seemingly contradictory results: http://arxiv.org/abs/1106.1066 via gamma-ray astronomy...