# Radioactivity and measurement

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Thread starter 6 years ago
#1
A sample of a radioactive element contains 1023 atoms. It is found that 3.5 x 1010 atoms decay in one day.

(a) Estimate the order of magnitude of the atoms that disintegrate in one second.
(b) What is the ratio of the original atoms to the atoms that remain after one day in orders of magnitude?

Since radioactive elements have a half life, don't I need that to find the answers?
Also, 3.5 x 1010 atoms will not always decay in one day right? the number will change as the sample halves and halves.
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6 years ago
#2
(Original post by Aaradhana)
A sample of a radioactive element contains 1023 atoms. It is found that 3.5 x 1010 atoms decay in one day.

(a) Estimate the order of magnitude of the atoms that disintegrate in one second.
(b) What is the ratio of the original atoms to the atoms that remain after one day in orders of magnitude?

Since radioactive elements have a half life, don't I need that to find the answers?
Also, 3.5 x 1010 atoms will not always decay in one day right? the number will change as the sample halves and halves.
This question has nothing to do with half life. It is to do with the decay in that particular day.

1) You know how many decay in a day, so how many secobds are there in a day.

2) How many atoms decay after this time, and how many are left. Find the ratio between the orders of magnitude of the two.

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Thread starter 6 years ago
#3
(Original post by majmuh24)
This question has nothing to do with half life. It is to do with the decay in that particular day.

1) You know how many decay in a day, so how many secobds are there in a day.

2) How many atoms decay after this time, and how many are left. Find the ratio between the orders of magnitude of the two.

Posted from TSR Mobile
The second one is obvious, but for the first one, the decay does not happen at a constant rate, right. So whatever answer we find for the number of atoms that disintegrate in a second, will only be an average and not the true answer, right?
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6 years ago
#4
(Original post by Aaradhana)
The second one is obvious, but for the first one, the decay does not happen at a constant rate, right. So whatever answer we find for the number of atoms that disintegrate in a second, will only be an average and not the true answer, right?
The activity of that substance is not going to change in one day*. So you just divide the disintegrations in one day by the number of seconds in a day.

* The half life is extremely long (Work it out!). The activity change in one day would be too small to measure.
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Thread starter 6 years ago
#5
(Original post by Stonebridge)
The activity of that substance is not going to change in one day*. So you just divide the disintegrations in one day by the number of seconds in a day.

* The half life is extremely long (Work it out!). The activity change in one day would be too small to measure.
Oh OK I see... wow I didn't think of that! Thanks a lot!
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