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Rate of Decay
Transcript of Rate of Decay
Radioactive nuclear decay is not predictable. One cannot predict when a nucleus will decay. But it does follow a probability. We call this stochastic. We can record and analyse and predict an overall radioactivity
We need to define some terms:
Number of particles (often radioactive particles)
Decays, number of particles that have decayed
Decay rate, or activity. number of particles that decay per second
Decay constant, describes individual rates of decay; per second)
Half life, time for half of the radioactive material to decay
Radioactivity follows a logarithmic function. This is true for the amount of material present, as well as the activity rates.
This equation describes the amount of radiative material present. The next is similar but shows the activity as it changes in time.
From the first we can define the half life from the radioactive constant as:
What is its radiative constant?
If a radioactive material has a half life of 20.5 minutes:
If an initial sample has particles, how many are left in 2 hours?
1.7% remaining ~ 6 halve lives
An ancient wooden club is found that contains 290 g of carbon and has an activity of 8.0 decays per second. Determine the age assuming that in living trees the ratio of C-14 / C-12 is 1.3x10^-12. (5730 years)
C 14 atoms