# BMAT/physics question

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#1
How do I even start from here? I didn't take Alevel physics, any help would be appreciated
Two radioactive sources X and Y have half-lives of 4.8 hours and 8.0 hours, respectively. Both
decay directly to form only stable isotopes.
The activity of a sample of the source X is measured by a detector as 320 counts per minute,
and simultaneously the radioactivity of a sample of the source Y is measured as 480 counts per
minute. Immediately after the measurements, the two samples are combined.
What is the count rate when the activity of the combination of X and Y is measured 24 hours
later?
[Assume that all readings in this question have been corrected for background radiation.]
A 25 counts per minute
B 50 counts per minute
C 55 counts per minute
D 70 counts per minute
E 100 counts per minute
F 140 counts per minute
0
3 weeks ago
#2
first of all BMAT questions for section two is based on gcse sciences and maths not a level.
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#3
(Original post by future-doctor <3)
first of all BMAT questions for section two is based on gcse sciences and maths not a level.
could you possibly still explain the steps to me?
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3 weeks ago
#4
you'll be expected to calculate based on the number of half lives in 24 hours

24/4.8 = 5 so the 320 cpm source goes through 5 half lives

after one half life it will be producing 160 cpm
after two half lifes it will be producing 80 cpm
after three half lifes it will be producing 40 cpm

etc

and the same for the other source using it's initial activity and the number of times its 8h half life goes into 24h
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