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Thread: ALPHA particle

  1. #1 ALPHA particle 
    Forum Freshman dheeraj's Avatar
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    hello guys...

    i've somehow read that speed of an alpha particle is 1,500 kilomet/sec

    an idea about how the speed of an alpha particle is calculated?

    what i thought earlier was since alpha particle consists of 2 protons and two neutrons if we know the speed of a helium atom
    considering the vanderwaal forces and the proton-electron attractions and eliminating it all we have left is the nucleus of the helium atom which is nothing but an alpha particle? correct me if my consideration or assumption was wrong.


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  3. #2  
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    alpha particle speed can vary between but use k.e=1/2mv^2


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    move this thread to physics
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  5. #4  
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    Quote Originally Posted by dheeraj View Post
    hello guys...

    i've somehow read that speed of an alpha particle is 1,500 kilomet/sec

    an idea about how the speed of an alpha particle is calculated?

    what i thought earlier was since alpha particle consists of 2 protons and two neutrons if we know the speed of a helium atom
    considering the vanderwaal forces and the proton-electron attractions and eliminating it all we have left is the nucleus of the helium atom which is nothing but an alpha particle? correct me if my consideration or assumption was wrong.
    What makes you think an alpha particle, or a helium atom, has a "speed"?

    If you know anything about kinetic theory, you should know that the speed of molecules making up a bulk substance (solid, liquid or gas) depends on the temperature. There is no set speed.

    If you are unfamiliar with the kinetic theory, try this: Kinetic theory - Wikipedia, the free encyclopedia

    Just the text in the first part will do. The maths lower down expresses the relationships between the micro-level behaviour and macro-level properties quantitatively, but this is not required to understand the principle.

    When it comes to individual particles that do not make up bulk matter, e.g. alpha particles, then bulk properties are undefined, but the speed is still a function of their energy. In this case it will be determined by the source of the particles, i.e. how energetically they were ejected by it.
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    Brassica oleracea Strange's Avatar
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    The speed is related to the half life of the emission process (which is surprising but then not surprising when you think about it)

    Quote Originally Posted by Wikipedia
    The energy of alpha particles emitted varies, with higher energy alpha particles being emitted from larger nuclei, but most alpha particles have energies of between 3 and 7 MeV (mega-electron-volts), corresponding to extremely long and extremely short half-lives of alpha-emitting nuclides, respectively.

    This energy is a substantial amount of energy for a single particle, but their high mass means alpha particles have a lower speed (with a typical kinetic energy of 5 MeV; the speed is 15,000 km/s, which is 5% of the speed of light) than any other common type of radiation
    Alpha particle - Wikipedia, the free encyclopedia
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    ei incumbit probatio qui dicit, non qui negat
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  7. #6  
    Forum Freshman dheeraj's Avatar
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    i know about kinetic theory of gases you have a point and i do agree with that, but it's like you're saying that a helium won't be having any speed.
    in kinetic theory of gases also the speed of the gas is the speed possessed by the max no individual gas molecules. so i don't think your question is appropriate :P
    anyway thanks for the reply
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    Forum Freshman dheeraj's Avatar
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    i get it now strange.
    thanks for the link. it was really very helpful and it do makes sense abt the thing (The energy of alpha particles emitted varies, with higher energy alpha particles being emitted from larger nuclei)

    again any idea how the energy is calculated by using e=m * c^2 ah?
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  9. #8  
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    Quote Originally Posted by dheeraj View Post
    i know about kinetic theory of gases you have a point and i do agree with that, but it's like you're saying that a helium won't be having any speed.
    in kinetic theory of gases also the speed of the gas is the speed possessed by the max no individual gas molecules. so i don't think your question is appropriate :P
    anyway thanks for the reply
    I'm glad you found Strange's explanation helpful.
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  10. #9  
    Brassica oleracea Strange's Avatar
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    Quote Originally Posted by dheeraj View Post
    again any idea how the energy is calculated by using e=m * c^2 ah?
    This isn't a subject I know a lot about, but I don't think this would be particularly significant in alpha emission. But basically, there will be a difference between the mass of the original atom and the mass of resulting atom + alpha particle. This difference will be accounted for in the kinetic energy of the alpha particle. I think this mass (energy) difference is much greater in fission (or fusion) reactions.
    ei incumbit probatio qui dicit, non qui negat
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