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#1
Hi everyone,

I would be grateful could help me out on this question that I've been stuck on for a while now on radioactivity in A2 level physics, or just a point in the right direction would be appreciated!

So here it is:

A radioactive sample, whose disintegration product is stable, was known to have an activity of 5x10^11 Bq at a certain time.

At that time an alpha particle detector showed a count rate of 32 per second.

Exactly 10 days later the rate had dropped to 8 per second.

Question:

a) Find the half life, the decay constant and the number of radioactive nuclei present in the sample at the start.

I thought you would start by finding the decay constant, but I just can't see the way to do it.

Thank you :-)
0
6 years ago
#2
(Original post by asha1494)
Hi everyone,

I would be grateful could help me out on this question that I've been stuck on for a while now on radioactivity in A2 level physics, or just a point in the right direction would be appreciated!

So here it is:

A radioactive sample, whose disintegration product is stable, was known to have an activity of 5x10^11 Bq at a certain time.

At that time an alpha particle detector showed a count rate of 32 per second.

Exactly 10 days later the rate had dropped to 8 per second.

Question:

a) Find the half life, the decay constant and the number of radioactive nuclei present in the sample at the start.

I thought you would start by finding the decay constant, but I just can't see the way to do it.

Thank you :-)
You have the count rate dropping by in 10 days.

What does that tell you?

Formula for decay constant involving half life is?

Finally use the formula for activity and number of nuclei.
0
6 years ago
#3
(Original post by Phichi)
You have the count rate dropping by in 10 days.

What does that tell you?

Formula for decay constant involving half life is?

Finally use the formula for activity and number of nuclei.
Could you use C=Co e-(decay constant)(t) and re arrange to find the decay constant?
0
6 years ago
#4
(Original post by MSB47)
Could you use C=Co e-(decay constant)(t) and re arrange to find the decay constant?
I would suggest the following:

Use the information about the count rate quartering over 10 days to find the half life. Then use to find the decay constant.

Then finally, for the initial number of nuclei.

If you haven't seen these equations before, let me know.
0
6 years ago
#5
(Original post by Phichi)
I would suggest the following:

Use the information about the count rate quartering over 10 days to find the half life. Then use to find the decay constant.

Then finally, for the initial number of nuclei.

If you haven't seen these equations before, let me know.
Oh ok that seems more straight forward but would the other way work too?
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