radioactivity Watch

FARAH NASEEM
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helpppp plzzzz some one tell me how to calculate the half life of nuclei , i am stuck with it plzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz zzzzzzzzzzzz help .
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Cora Lindsay
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Half life is the time required for the number of nuclei to decrease to half of its initial value, or the radioactive decay rate to decrease to half the initial decay rate (because decay rate is proprtional to numnber of nuclei)

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Dualcore
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(Original post by FARAH NASEEM)
helpppp plzzzz some one tell me how to calculate the half life of nuclei , i am stuck with it plzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz zzzzzzzzzzzz help .
assuming you are given the decay constant it will be half life=ln(2)/decay constant
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FARAH NASEEM
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(Original post by Cora Lindsay)
Half life is the time required for the number of nuclei to decrease to half of its initial value, or the radioactive decay rate to decrease to half the initial decay rate (because decay rate is proprtional to numnber of nuclei)

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okay so here is a question plzz help me solving that

The half -life of a radioisotope is 2400 years . The activity of a sample is 720 counts/s .How long it take for the activity to fall to 90 counts/s .
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Daniel F
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720/90=8
8=2^3
Therefore the total number of half-lives is 3.
3x2400=7200
Total number of years is 7200 years.


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uberteknik
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(Original post by FARAH NASEEM)
okay so here is a question plzz help me solving that

The half -life of a radioisotope is 2400 years . The activity of a sample is 720 counts/s .How long it take for the activity to fall to 90 counts/s .
This is a GCSE question. The calculations and answers are going to be simple integer values - guaranteed.

So Start with 720 counts per second as the baseline:

After 2400 years the counts will fall to 720/2 = 360 counts per second. i.e. half the nuclei have decayed so producing only half the number of counts per second after that time.

After another 2400 years (2400 + 2400 = 4800 years total ) the counts will fall to 360/2 = 180 counts per second.

After another 2400 years (2400 + 2400 + 2400 = 7200 years total) the counts will fall to 180/2 = 90 counts per second.

And there is your answer.

It takes 7200 years for the radio-isotope with a half life of 2400 years and an initial activity of 720 counts per second, to decay to 90 counts per second.
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FARAH NASEEM
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(Original post by uberteknik)
This is a GCSE question. The calculations and answers are going to be simple integer values - guaranteed.

So Start with 720 counts per second as the baseline:

After 2400 years the counts will fall to 720/2 = 360 counts per second. i.e. half the nuclei have decayed so producing only half the number of counts per second after that time.

After another 2400 years (2400 + 2400 = 4800 years total ) the counts will fall to 360/2 = 180 counts per second.

After another 2400 years (2400 + 2400 + 2400 = 7200 years total) the counts will fall to 180/2 = 90 counts per second.

And there is your answer.

It takes 7200 years for the radio-isotope with a half life of 2400 years and an initial activity of 720 counts per second, to decay to 90 counts per second.
awwwwwwww thanks alot
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