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Activity of a radioactive substance decreases from 8000BQ ato 1000Bq in 9 days.What is half life and average life of radoactive substance

Bhubesh , 10 Years ago

Grade 12

1 Answers

Chandra Chatterjee

Last Activity: 10 Years ago

Let A be the new activity and A’ be the original activity

Now there is a formula (A/A’) = (1/2)^(t/T). Where t is the given time and T is the half life. (I am not showing the derivation. It will become long. U can refer to any good book)

Now it's given A=1000 A’=8000 t=9. Therefore (1000/8000)=(1/2)^9/T

Or, (1/2)^3=(1/2)^9/T. So 3= 9/T So T=3. Then comes average life. Here also there is a simple relation between average life T.. and half life T that is T..= 1.44T. So avg life is 4.32days.

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