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I What does it mean when they say half life of a neutron

  1. Nov 19, 2016 #1
    My book says that a free neutron, unlike a free proton is unstable. It decays into proton, electron and a antineutrino, and has half life of about 1000s.

    I do not understand how a single particle can have something called half life. I am finding difficulty to think of a proton being reduced in mass with time and it takes some time like 1000 second to become half!!!

    For me the moment neutron losses any of its properties( mass etc) it no more remains a neutron. I mean a single particle should simply be either exist or converted into something. I am unable to think what it actually would mean when they say it's half like is 1000s.

    Thank a bunch.
  2. jcsd
  3. Nov 19, 2016 #2


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    If you have many neutrons, the half life is the time when half of of them will be gone. It is not something to apply to a single neutron except in questions about the probability that it will still be there after a certain amount of time.
  4. Nov 19, 2016 #3


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    An individual neutron decays after some random amount of time. It is a neutron before it decays, it is not a neutron any more after the decay.

    The half-life tells you, on average, how long neutrons stay neutrons before the decay happens: 50% of all neutrons decay in the first 1000 seconds.
  5. Nov 19, 2016 #4


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    ...whereupon 50% of the remaining 50% decay in the next 1000 seconds, leaving 25% of the original amount;
    whereupon 50% of the remaining 25% decay in the next 1000 seconds, etc. etc.
  6. Nov 19, 2016 #5


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    If I tell you that a population of 20,000 people has a mean lifetime of 75 years, what information can you obtain for a single person taken out of that population?
  7. Nov 27, 2016 #6
    Thank you got it.

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