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Half life and exponential decay

Half life and exponential decay.  - Per second probability of a nuclei decaying (s -1 ) N - Number of un-decayed nuclei (number) A = Activity - decays/sec (s -1 ) A = -N / t N = N o e -t - Exponential decay N o - Original value N - Value at time t t - Elapsed time Diff EQ…

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Half life and exponential decay

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  1. Half life and exponential decay •  - Per second probability of a nuclei decaying (s-1) • N - Number of un-decayed nuclei (number) • A = Activity - decays/sec (s-1) • A = -N/t • N = Noe-t - Exponential decay • No - Original value • N - Value at time t • t - Elapsed time • Diff EQ… • A = N = Noe-t

  2. Half life T1/2 - Half life - time for half nuclei to decay

  3. Half life and exponential decay A = N = Noe-t A = -N/t N = Noe-t T1/2 = ln(2)/ Half lives occur over and over Half life here is 20 s

  4. Bi 211 has a half life of 128.4 s. What is the per-second probability of a nuclei decaying? If you start out with 32 grams of Bi 211, how much is left after 385.2 s? After what time is there 23 grams left? What is the activity when there is 23 grams left? (m = 210.987 u) (4.0 g, 61 s, 3.54E+20 Bq) Example: A = N = Noe-t A = -N/t N = Noe-t T1/2 = ln(2)/

  5. Oregonium has a decay probability of 8.91 x 10-8 s-1. What is its half life in days? 90.0 days

  6. What is the nuclear decay probability of a substance that has a half life of 96.23 minutes? 0.0001201 s-1

  7. Oregonium has a decay probability of 8.91 x 10-8 s-1. If you have 1250 grams of Oregonium initially, how many grams do you have after 30.00 days? (x24x3600) 992 g

  8. Tualatonium has a half life of 12 seconds. If you start with 64 grams of it, how much remains after a minute? (Cheat) 2.0 grams

  9. Tigardium has a half life of 8.34 seconds. The initial activity is 1350 counts/second, after what time is the activity 125 counts/sec? 28.6 s

  10. A certain substance has an activity of 1245 counts/sec initially, and an activity of 938 counts/second after exactly 3.00 minutes. What is the half life of the substance? 441 s

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