A bomb, what's actually happening?

  1. Take a hydrogen bomb. The instant after the atom is split, what happens? I always imagined it as the protons and neutrons stay in tact, but the separation of their strong force bonds releases a bunch of energy in the form of EM radiation. But how does a bunch of EM radiation cause such huge shock waves and damage? Or in TNT, there is a chemical reaction and the through conservation of energy, a lot of EM radiation is produced. What is actually doing the damage to your body if you are near an explosion?
  2. jcsd
  3. Expanding gasses.
  4. What about a hydrogen bomb in space?
  5. Nugatory

    Staff: Mentor

    Much of the energy is released in the form of heat. The heat expands the air (and vaporized bits of bomb) very rapidly, enormously increasing its pressure, and that's what creates the blast wave.
  6. Which is, as I said, expanding gasses :smile:
  7. Nugatory

    Staff: Mentor

    No shock wave, but very intense radiation. Flash effects are more pronounced, blast effects less pronounced. Even flash effects can produce substantial shock damage - the radiation from a nuclear weapon can heat the surface of a nearby object so that it vaporizes, and the expanding vapors do as much damage as if the surface had exploded.
  8. Nugatory

    Staff: Mentor

    Yep - our posts crossed.
  9. A.T.

    A.T. 6,455
    Science Advisor
    Gold Member

  10. Nugatory

    Staff: Mentor

    Google for "nuclear weapons effects" will find much more on this (morbidly fascinating) subject.
  11. jtbell

    Staff: Mentor

    An H-bomb uses fusion, not fission.
  12. SteamKing

    SteamKing 10,932
    Staff Emeritus
    Science Advisor
    Homework Helper

    There are two types of nuclear weapon: the fission device, more commonly known as the A-bomb, and the fusion device, also known as a hydrogen bomb, or H-bomb.



    In an A-bomb, a critical mass of U-235 or Pu-239 undergoes a chain-reaction, where the atoms of uranium or plutonium are split into smaller pieces. In an H-bomb, varying amounts of deuterium or tritium, isotopes of hydrogen, undergo fusion into helium.

    The reactions in the nuclear bombs release a large amount of energy within a fraction of a second. This enormous energy heats the surrounding atmosphere, which wants to rapidly expand as a result. The atmosphere does indeed expand, reaching supersonic velocities in the immediate vicinity of the blast, and slowing as the shock wave expands around the explosion. This shock wave creates a zone of high pressure, which is able to destroy or damage structures on the ground.

    Some of the energy from the blast is released in the form of gamma rays, which can't travel very far in the atmosphere, but which rays are then converted to X-rays, which can travel large distances, since the atmosphere is essentially transparent to this form of radiation.

    People on the ground near a nuclear explosion are injured or killed either due to the effects of being exposed to the heat of the blast, being exposed to a high dose of radiation, or are hit by flying debris or trapped within a collapsing structure.

    TNT, or trinitrotoluene, is a chemical explosive. When it detonates, the result is a very fast-moving reaction where the TNT chemically decomposes.


    Unlike a nuclear device, a TNT explosion produces no lethal EM-radiation. This type of explosion generates a very-fast moving shock wave in the atmosphere, the over-pressure from which can destroy structures and cause lethal injuries to people in the immediate vicinity. Think of TNT as a more sophisticated version of gunpowder.
  13. Oh ya, truth.

    Interesting stuff guys, thanks.
  14. nsaspook

    nsaspook 1,378
    Science Advisor

    It's fascinating until you have to watch hours and hours of old film on the subject for some class in school. :frown:
  15. Drakkith

    Staff: Mentor

    Not true. H-bombs always have a fission primary stage. In addition, the fusion secondary is typically surrounded by a "pusher" made of uranium which undergoes fission itself and ends up producing up to half of the explosive energy of the bomb.

    From wiki: http://en.wikipedia.org/wiki/Thermonuclear_weapon

    A thermonuclear weapon is a nuclear weapon design that uses the heat generated by a fission reaction to compress and ignite a nuclear fusion stage. This results in greatly increased explosive power. It is colloquially referred to as a hydrogen bomb or H-bomb because it employs hydrogen fusion, though in most applications the majority of its destructive energy comes from uranium fission, not hydrogen fusion alone. The fusion stage in such weapons is required to efficiently cause the large quantities of fission characteristic of most thermonuclear weapons.


    The fusion fuel of the secondary stage may be surrounded by depleted uranium or natural uranium, whose U-238 is not fissile and cannot sustain a chain reaction, but which is fissionable when bombarded by the high-energy neutrons released by fusion in the secondary stage. This process provides considerable energy yield (as much as half of the total yield in large devices), but is not considered a tertiary "stage".
  16. mfb

    Staff: Mentor

    Both in nuclear and conventional explosions, most (not all) electromagnetic radiation is just a by-product created after the "main process" happens.
    The released energy is usually released as kinetic energy of the reaction products. Those products then heat the material around them in collisions. And hot materials emit electromagnetic radiation.
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